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Sample records for gas hydrate resources

  1. Gas hydrate resources of northern Alaska

    USGS Publications Warehouse

    Collett, T.S.

    1997-01-01

    Large amounts of natural gas, composed mainly of methane, can occur in arctic sedimentary basins in the form of gas hydrates under appropriate temperature and pressure conditions. Gas hydrates are solids, composed of rigid cages of water molecules that trap molecules of gas. These substances are regarded as a potential unconventional source of natural gas because of their enormous gas-storage capacity. Most published gas hydrate resource estimates are highly simplified and based on limited geological data. The gas hydrate resource assessment for northern Alaska presented in this paper is based on a "play analysis" scheme, in which geological factors controlling the accumulation and preservation of gas hydrates are individually evaluated and risked for each hydrate play. This resource assessment identified two gas hydrate plays; the in-place gas resources within the gas hydrates of northern Alaska are estimated to range from 6.7 to 66.8 trillion cubic metres of gas (236 to 2,357 trillion cubic feet of gas), at the 0.50 and 0.05 probability levels respectively. The mean in-place hydrate resource estimate for northern Alaska is calculated to be 16.7 trillion cubic metres of gas (590 trillion cubic feet of gas). If this assessment is valid, the amount of natural gas stored as gas hydrates in northern Alaska could be almost seven times larger then the estimated total remaining recoverable conventional natural gas resources in the entire United States.

  2. Energy resource potential of natural gas hydrates

    USGS Publications Warehouse

    Collett, T.S.

    2002-01-01

    The discovery of large gas hydrate accumulations in terrestrial permafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved before gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m3. Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.

  3. Prospecting for marine gas hydrate resources

    USGS Publications Warehouse

    Boswell, Ray; Shipp, Craig; Reichel, Thomas; Shelander, Dianna; Saeki, Tetsuo; Frye, Matthew; Shedd, William; Collett, Timothy S.; McConnell, Daniel R.

    2016-01-01

    As gas hydrate energy assessment matures worldwide, emphasis has evolved away from confirmation of the mere presence of gas hydrate to the more complex issue of prospecting for those specific accumulations that are viable resource targets. Gas hydrate exploration now integrates the unique pressure and temperature preconditions for gas hydrate occurrence with those concepts and practices that are the basis for conventional oil and gas exploration. We have aimed to assimilate the lessons learned to date in global gas hydrate exploration to outline a generalized prospecting approach as follows: (1) use existing well and geophysical data to delineate the gas hydrate stability zone (GHSZ), (2) identify and evaluate potential direct indications of hydrate occurrence through evaluation of interval of elevated acoustic velocity and/or seismic events of prospective amplitude and polarity, (3) mitigate geologic risk via regional seismic and stratigraphic facies analysis as well as seismic mapping of amplitude distribution along prospective horizons, and (4) mitigate further prospect risk through assessment of the evidence of gas presence and migration into the GHSZ. Although a wide range of occurrence types might ultimately become viable energy supply options, this approach, which has been tested in only a small number of locations worldwide, has directed prospect evaluation toward those sand-hosted, high-saturation occurrences that were presently considered to have the greatest future commercial potential.

  4. Natural gas hydrates; vast resource, uncertain future

    USGS Publications Warehouse

    Collett, T.S.

    2001-01-01

    Gas hydrates are naturally occurring icelike solids in which water molecules trap gas molecules in a cagelike structure known as a clathrate. Although many gases form hydrates in nature, methane hydrate is by far the most common; methane is the most abundant natural gas. The volume of carbon contained in methane hydrates worldwide is estimated to be twice the amount contained in all fossil fuels on Earth, including coal.

  5. Development of Alaskan gas hydrate resources

    SciTech Connect

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  6. Seismic reflections identify finite differences in gas hydrate resources

    USGS Publications Warehouse

    Dillon, W.; Max, M.

    1999-01-01

    What processes control methane hydrate concentrations? Gas hydrate occurs naturally at the pressure/ temperature/chemical conditions that are present within ocean floor sediments at water depths greater than about 500 meters. The gas hydrate stability zone (GHSZ) extends from the sea bottom downward to a depth where the natural increase in temperature causes the hydrate to melt (dissociate), even though the downward pressure increase is working to increase gas hydrate stability. Thus, the base of the GHSZ tends to parallel the seafloor at any given water depth (pressure), because the sub-seafloor isotherms (depths of constant temperature) generally parallel the seafloor. The layer at which gas hydrate is stable commonly extends from the sea floor to several hundred meters below it. The gas in most gas hydrates is methane, generated by bacteria in the sediments. In some cases, it can be higher carbon-number, thermogenic hydrocarbon gases that rise from greater depths.

  7. Development of Alaskan gas hydrate resources. Final report

    SciTech Connect

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  8. Results at Mallik highlight progress in gas hydrate energy resource research and development

    USGS Publications Warehouse

    Collett, T.S.

    2005-01-01

    The recent studies that project the role of gas hydrates in the future energy resource management are reviewed. Researchers have long speculated that gas hydrates could eventually be a commercial resource for the future. A Joint Industry Project led by ChevronTexaco and the US Department of Energy is designed to characterize gas hydrates in the Gulf of Mexico. Countries including Japan, canada, and India have established large gas hydrate research and development projects, while China, Korea and Mexico are investigating the viability of forming government-sponsored gas hydrate research projects.

  9. Natural-gas hydrates: Resource of the twenty-first century?

    USGS Publications Warehouse

    Collett, T.S.

    2001-01-01

    Although considerable uncertainty and disagreement prevail concerning the world's gas-hydrate resources, the estimated amount of gas in those gas-hydrate accumulations greatly exceeds the volume of known conventional gas reserves. However, the role that gas hydrates will play in contributing to the world's energy requirements will ultimately depend less on the volume of gas-hydrate resources than on the cost to extract them. Gas hydrates occur in sedimentary deposits under conditions of pressure and temperature present in permafrost regions and beneath the sea in outer continental margins. The combined information from arctic gas-hydrate studies shows that in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 m to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors (known as bottom-simulating reflectors) that have been mapped at depths below the seafloor ranging from approximately 100 m to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas-hydrate accumulations are in rough accord at about 20,000 trillion m3. Gas hydrate as an energy commodity is often grouped with other unconventional hydrocarbon resources. In most cases, the evolution of a nonproducible unconventional resource to a producible energy resource has relied on significant capital investment and technology development. To evaluate the energy-resource potential of gas hydrates will also require the support of sustained research and development programs. Despite the fact that relatively little is known about the ultimate resource potential of gas hydrates, it is certain that they are a vast storehouse of natural gas, and significant technical challenges will need to be met before this enormous resource can be considered an economically producible reserve.

  10. Gas hydrate and humans

    USGS Publications Warehouse

    Kvenvolden, K.A.

    2000-01-01

    The potential effects of naturally occurring gas hydrate on humans are not understood with certainty, but enough information has been acquired over the past 30 years to make preliminary assessments possible. Three major issues are gas hydrate as (1) a potential energy resource, (2) a factor in global climate change, and (3) a submarine geohazard. The methane content is estimated to be between 1015 to 1017 m3 at STP and the worldwide distribution in outer continental margins of oceans and in polar regions are significant features of gas hydrate. However, its immediate development as an energy resource is not likely because there are various geological constraints and difficult technological problems that must be solved before economic recovery of methane from hydrate can be achieved. The role of gas hydrate in global climate change is uncertain. For hydrate methane to be an effective greenhouse gas, it must reach the atmosphere. Yet there are many obstacles to the transfer of methane from hydrate to the atmosphere. Rates of gas hydrate dissociation and the integrated rates of release and destruction of the methane in the geo/hydro/atmosphere are not adequately understood. Gas hydrate as a submarine geohazard, however, is of immediate and increasing importance to humans as our industrial society moves to exploit seabed resources at ever-greater depths in the waters of our coastal oceans. Human activities and installations in regions of gas-hydrate occurrence must take into account the presence of gas hydrate and deal with the consequences of its presence.

  11. Development of Alaskan gas hydrate resources: Annual report, October 1986--September 1987

    SciTech Connect

    Sharma, G.D.; Kamath, V.A.; Godbole, S.P.; Patil, S.L.; Paranjpe, S.G.; Mutalik, P.N.; Nadem, N.

    1987-10-01

    Solid ice-like mixtures of natural gas and water in the form of natural gas hydrated have been found immobilized in the rocks beneath the permafrost in Arctic basins and in muds under the deep water along the American continental margins, in the North Sea and several other locations around the world. It is estimated that the arctic areas of the United States may contain as much as 500 trillion SCF of natural gas in the form of gas hydrates (Lewin and Associates, 1983). While the US Arctic gas hydrate resources may have enormous potential and represent long term future source of natural gas, the recovery of this resource from reservoir frozen with gas hydrates has not been commercialized yet. Continuing study and research is essential to develop technologies which will enable a detailed characterization and assessment of this alternative natural gas resource, so that development of cost effective extraction technology.

  12. The methane hydrate formation and the resource estimate resulting from free gas migration in seeping seafloor hydrate stability zone

    NASA Astrophysics Data System (ADS)

    Guan, Jinan; Liang, Deqing; Wu, Nengyou; Fan, Shuanshi

    2009-10-01

    It is a typical multiphase flow process for hydrate formation in seeping seafloor sediments. Free gas can not only be present but also take part in formation of hydrate. The volume fraction of free gas in local pore of hydrate stable zone (HSZ) influences the formation of hydrate in seeping seafloor area, and methane flux determines the abundance and resource of hydrate-bearing reservoirs. In this paper, a multiphase flow model including water (dissolved methane and salt)-free gas hydrate has been established to describe this kind of flow-transfer-reaction process where there exists a large scale of free gas migration and transform in seafloor pore. In the order of three different scenarios, the conversions among permeability, capillary pressure, phase saturations and salinity along with the formation of hydrate have been deducted. Furthermore, the influence of four sorts of free gas saturations and three classes of methane fluxes on hydrate formation and the resource has also been analyzed and compared. Based on the rules drawn from the simulation, and combined information gotten from drills in field, the methane hydrate(MH) formation in Shenhu area of South China Sea has been forecasted. It has been speculated that there may breed a moderate methane flux below this seafloor HSZ. If the flux is about 0.5 kg m -2 a -1, then it will go on to evolve about 2700 ka until the hydrate saturation in pore will arrive its peak (about 75%). Approximately 1.47 × 10 9 m 3 MH has been reckoned in this marine basin finally, is about 13 times over preliminary estimate.

  13. Assessment of Gas Hydrate Resources on the North Slope, Alaska, 2008

    NASA Astrophysics Data System (ADS)

    Collett, T. S.

    2008-12-01

    At the 2008 Fall Meeting of the American Geophysical Union, the USGS will release the results of the first assessment of the undiscovered technically recoverable gas hydrate resources on the North Slope of Alaska. This assessment indicates the existence of technically recoverable gas hydrate resources -- that is, resources that can be discovered, developed, and produced by using current technology. The assessment is based on the geologic elements used to define a Total Petroleum System (TPS), including hydrocarbon source rocks (source-rock type and maturation and hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy, petrophysical properties, seismic attribute development, and prospecting), and hydrocarbon traps (trap formation and timing). The area assessed in northern Alaska extends from the National Petroleum Reserve in Alaska (NPRA) on the west through the Arctic National Wildlife Refuge (ANWR) on the east and from the Brooks Range northward to the State-Federal offshore boundary (located about 4.8 km north of the coastline). This area consists mostly of Federal, State, and Native lands covering about 114,765 square km. For the first time, the USGS has assessed gas hydrates, a traditionally unconventional resource with no confirmed production history, as a producible resource occurring in discrete hydrocarbon traps and structures. The approach used to assess the gas hydrate resources in northern Alaska followed standard geology-based USGS assessment methodologies developed to assess conventional oil and gas resources. In order to use the USGS conventional assessment approach on gas hydrate resources, it was documented through the analysis of three-dimensional industry-acquired seismic data that the gas hydrates on the North Slope occupy limited, discrete volumes of rock bounded by faults and downdip water contacts. The USGS conventional assessment approach also assumes that the hydrocarbon resource being assessed can be produced by

  14. Gas hydrates as potential resource of energy and pathfinders for conventional type hydrocarbon deposits

    SciTech Connect

    Krason, J. )

    1991-03-01

    Solid compounds of water and gaseous hydrocarbons are known as gas hydrates, clathrates, or cryohydrates. They occur naturally in offshore and terrestrial environments, in the areas where temperature is at least seasonally low (i.e. close to or below freezing), bathymetric, geostatic, ice, or permafrost pressure is sufficiently high, and the source of hydrocarbons is available. These factors (regional and local geological conditions of 21 locations grouped into 13 study regions worldwide offshore and one in permafrost environments with proven, reported, and inferred presence of gas hydrates) have been recently researched by Geoexplorers International, Inc. Conservative estimations from Geoexplorers International suggest that the world's total gas hydrates may contain 7,000 to 50,000 tcf of natural gas. Although at this time exploitation of gas trapped in the hydrate zone and below is not economically viable, because estimated reserves are enormous, they should be seriously considered as potential energy resource. Smaller, but less dispersed massive gas hydrate deposits associated with fault zones may be the first offshore gas resource to become economic. This research, particularly of the Messoyakh gas field, has proved that the presence of gas hydrates provides very useful information in exploration for conventional oil and gas deposits. Gas hydrates indicate ongoing hydrocarbon generation in the sediments. Hydrates are valuable to assess the present heat flow and thermal history of a region. Since gas hydrates exist only under a very limited range of pressure and temperature, deviation in patterns of their occurrence can be related to changes in pore water chemistry, hydrocarbon composition, or pressure and temperature gradient anomalies.

  15. Natural gas hydrates of Circum-Pacific margin-a future energy resource

    SciTech Connect

    Kvenvolden, K.A.; Cooper, A.K.

    1986-07-01

    Natural gas hydrates are probably present within the uppermost 1100 m (3600 ft) of oceanic sediment in the following regions of outer continental margins rimming the Pacific Ocean basin: (1) the continental slope east of the North Island of New Zealand; (2) the landward slope of the Nankai Trough off Japan; (3) the continental slope of the northwestern and eastern Aleutian Trench; (4) the continental slope off northern California; (5) the landward slope of the Middle America Trench off Central America; (6) the landward slope of the Peru-Chile Trench; and (7) the basinal sediment of the Ross Sea and the continental margin off Wilkes Land, Antarctica. These gas hydrates likely contain and cap significant quantities of methane. Geophysical evidence for gas hydrates is found mainly in the widespread occurrence on marine seismic records of an anomalous reflection event that apparently marks the base of the gas-hydrate zone. Geochemical evidence consists of analyses of gases and interstitial fluids obtained from drilling in offshore sedimentary deposits, particularly at nine DSDP sites cored adjacent to the Middle America Trench where gas hydrates were recovered. Natural gas hydrates will probably be identified in many other Circum-Pacific regions as exploration for offshore petroleum moves into deeper waters over continental and island-arc slopes. Initially, these gas hydrates will probably not be considered as potential energy resources, but special drilling procedures may be needed to penetrate them safely. However, if appropriate reservoirs are found in association with the gas hydrates, then an important energy resource may be discovered.

  16. Regional Mapping and Resource Assessment of Shallow Gas Hydrates of Japan Sea - METI Launched 3 Years Project in 2013.

    NASA Astrophysics Data System (ADS)

    Matsumoto, R.

    2014-12-01

    Agency of Natural Resources and Energy of METI launched a 3 years shallow gas hydrate exploration project in 2013 to make a precise resource assessment of shallow gas hydrates in the eastern margin of Japan Sea and around Hokkaido. Shallow gas hydrates of Japan Sea occur in fine-grained muddy sediments of shallow subsurface of mounds and gas chimneys in the form of massive nodular to platy accumulation. Gas hydrate bearing mounds are often associated with active methane seeps, bacterial mats and carbonate concretions and pavements. Gases of gas hydrates are derived either from deep thermogenic, shallow microbial or from the mixed gases, contrasting with totally microbial deep-seated stratigraphically controlled hydrates. Shallow gas hydrates in Japan Sea have not been considered as energy resource due to its limited distribution in narrow Joetsu basin. However recently academic research surveys have demonstrated regional distribution of gas chimney and hydrate mound in a number of sedimentary basins along the eastern margin of Japan Sea. Regional mapping of gas chimney and hydrate mound by means of MBES and SBP surveys have confirmed that more than 200 gas chimneys exist in 100 km x 100 km area. ROV dives have identified dense accumulation of hydrates on the wall of half collapsed hydrate mound down to 30 mbsf. Sequential LWD and shallow coring campaign in the Summer of 2014, R/V Hakurei, which is equipped with Fugro Seacore R140 drilling rig, drilled through hydrate mounds and gas chimneys down to the BGHS (base of gas hydrate stability) level and successfully recovered massive gas hydrates bearing sediments from several horizons.

  17. Gas Hydrates on Mars: In-situ Resources for Human Habitation?

    NASA Astrophysics Data System (ADS)

    Max, M. D.; Pellenbarg, R. E.

    2002-05-01

    The apparent presence of abundant water on Mars, combined with the recent discovery of deep lithoautotrophic bacteria on Earth raises the possibility that a similar development of early life was established on Mars early in its history. CH4 would be a likely by-product of that deep biosphere metabolism. Where methane may have been produced over a long period of time, considerable volumes of it can be expected to have migrated toward the planet?s surface. Although confirmation of the presence of gas hydrate in the Martian subsurface has yet to be made, its occurrence is consistent with the temperature and pressure regimes expected at depth. The possible existence of substantial deposits of gas hydrates in the Martian subsurface, comparable to those now known on Earth, may be of critical importance to exploration and colonization of Mars because hydrate concentrates resources. Both CO2 and CH4 hydrates compress about 164 m3 of gas (at Earth STP) along with about 0.87m3 of pure water into each m3 of gas hydrate. The successful retrieval of concentrated CO2, CH4 and water from relatively shallow depths within the Martian cryosphere may provide the key of human occupation of Mars. In addition to the basic elements of fuel and water necessary to support the eventual expansion of human life across the surface of the planet virtually all shelter and hard goods can be fabricated from plastics produced from chemical components of these hydrate deposits.

  18. National Assessment of Oil and Gas Project: geologic assessment of undiscovered gas hydrate resources on the North Slope, Alaska

    USGS Publications Warehouse

    USGS AK Gas Hydrate Assessment Team: Collett, Timothy S.; Agena, Warren F.; Lee, Myung Woong; Lewis, Kristen A.; Zyrianova, Margarita V.; Bird, Kenneth J.; Charpentier, Ronald R.; Cook, Troy A.; Houseknecht, David W.; Klett, Timothy R.; Pollastro, Richard M.

    2014-01-01

    Scientists with the U.S. Geological Survey have completed the first assessment of the undiscovered, technically recoverable gas hydrate resources beneath the North Slope of Alaska. This assessment indicates the existence of technically recoverable gas hydrate resources—that is, resources that can be discovered, developed, and produced using current technology. The approach used in this assessment followed standard geology-based USGS methodologies developed to assess conventional oil and gas resources. In order to use the USGS conventional assessment approach on gas hydrate resources, three-dimensional industry-acquired seismic data were analyzed. The analyses indicated that the gas hydrates on the North Slope occupy limited, discrete volumes of rock bounded by faults and downdip water contacts. This assessment approach also assumes that the resource can be produced by existing conventional technology, on the basis of limited field testing and numerical production models of gas hydrate-bearing reservoirs. The area assessed in northern Alaska extends from the National Petroleum Reserve in Alaska on the west through the Arctic National Wildlife Refuge on the east and from the Brooks Range northward to the State-Federal offshore boundary (located 3 miles north of the coastline). This area consists mostly of Federal, State, and Native lands covering 55,894 square miles. Using the standard geology-based assessment methodology, the USGS estimated that the total undiscovered technically recoverable natural-gas resources in gas hydrates in northern Alaska range between 25.2 and 157.8 trillion cubic feet, representing 95 percent and 5 percent probabilities of greater than these amounts, respectively, with a mean estimate of 85.4 trillion cubic feet.

  19. Global occurrences of gas hydrate

    USGS Publications Warehouse

    Kvenvolden, K.A.; Lorenson, T.D.

    2001-01-01

    Natural gas hydrate is found worldwide in sediments of outer continental margins of all oceans and in polar areas with continuous permafrost. There are currently 77 localities identified globally where geophysical, geochemical and/or geological evidence indicates the presence of gas hydrate. Details concerning individual gas-hydrate occurrences are compiled at a new world-wide-web (www) site (http://walrus.wr.usgs.gov/globalhydrate). This site has been created to facilitate global gas-hydrate research by providing information on each of the localities where there is evidence for gas hydrate. Also considered are the implications of gas hydrate as a potential (1) energy resource, (2) factor in global climate change, and (3) geohazard.

  20. RESOURCE CHARACTERIZATION AND QUANTIFICATION OF NATURAL GAS-HYDRATE AND ASSOCIATED FREE-GAS ACCUMULATIONS IN THE PRUDHOE BAY - KUPARUK RIVER AREA ON THE NORTH SLOPE OF ALASKA

    SciTech Connect

    Robert Hunter; Shirish Patil; Robert Casavant; Tim Collett

    2003-06-02

    Interim results are presented from the project designed to characterize, quantify, and determine the commercial feasibility of Alaska North Slope (ANS) gas-hydrate and associated free-gas resources in the Prudhoe Bay Unit (PBU), Kuparuk River Unit (KRU), and Milne Point Unit (MPU) areas. This collaborative research will provide practical input to reservoir and economic models, determine the technical feasibility of gas hydrate production, and influence future exploration and field extension of this potential ANS resource. The large magnitude of unconventional in-place gas (40-100 TCF) and conventional ANS gas commercialization evaluation creates industry-DOE alignment to assess this potential resource. This region uniquely combines known gas hydrate presence and existing production infrastructure. Many technical, economical, environmental, and safety issues require resolution before enabling gas hydrate commercial production. Gas hydrate energy resource potential has been studied for nearly three decades. However, this knowledge has not been applied to practical ANS gas hydrate resource development. ANS gas hydrate and associated free gas reservoirs are being studied to determine reservoir extent, stratigraphy, structure, continuity, quality, variability, and geophysical and petrophysical property distribution. Phase 1 will characterize reservoirs, lead to recoverable reserve and commercial potential estimates, and define procedures for gas hydrate drilling, data acquisition, completion, and production. Phases 2 and 3 will integrate well, core, log, and long-term production test data from additional wells, if justified by results from prior phases. The project could lead to future ANS gas hydrate pilot development. This project will help solve technical and economic issues to enable government and industry to make informed decisions regarding future commercialization of unconventional gas-hydrate resources.

  1. Toward production from gas hydrates: Current status, assessment of resources, and simulation-based evaluation of technology and potential

    USGS Publications Warehouse

    Moridis, G.J.; Collett, T.S.; Boswell, R.; Kurihara, M.; Reagan, M.T.; Koh, C.; Sloan, E.D.

    2008-01-01

    Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international R&D programs, and the remaining science and technological challenges facing commercialization of production. After a brief examination of gas hydrate accumulations that are well characterized and appear to be models for future development and gas production, we analyze the role of numerical simulation in the assessment of the hydrate production potential, identify the data needs for reliable predictions, evaluate the status of knowledge with regard to these needs, discuss knowledge gaps and their impact, and reach the conclusion that the numerical simulation capabilities are quite advanced and that the related gaps are either not significant or are being addressed. We review the current body of literature relevant to potential productivity from different types of gas hydrate deposits, and determine that there are consistent indications of a large production potential at high rates over long periods from a wide variety of hydrate deposits. Finally, we identify (a) features, conditions, geology and techniques that are desirable in potential production targets, (b) methods to maximize production, and (c) some of the conditions and characteristics that render certain gas hydrate deposits undesirable for production. Copyright 2008, Society of Petroleum Engineers.

  2. Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluationof Technology and Potential

    SciTech Connect

    Reagan, Matthew; Moridis, George J.; Collett, Timothy; Boswell, Ray; Kurihara, M.; Reagan, Matthew T.; Koh, Carolyn; Sloan, E. Dendy

    2008-02-12

    Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international R&D programs, and the remaining science and technological challenges facing commercialization of production. After a brief examination of gas hydrate accumulations that are well characterized and appear to be models for future development and gas production, we analyze the role of numerical simulation in the assessment of the hydrate production potential, identify the data needs for reliable predictions, evaluate the status of knowledge with regard to these needs, discuss knowledge gaps and their impact, and reach the conclusion that the numerical simulation capabilities are quite advanced and that the related gaps are either not significant or are being addressed. We review the current body of literature relevant to potential productivity from different types of gas hydrate deposits, and determine that there are consistent indications of a large production potential at high rates over long periods from a wide variety of hydrate deposits. Finally, we identify (a) features, conditions, geology and techniques that are desirable in potential production targets, (b) methods to maximize production, and (c) some of the conditions and characteristics that render certain gas hydrate deposits undesirable for production.

  3. Stable Gas Hydrates Beneath a BSR: Implications for Resource Inventories and Shallow Hydrocarbon Fluid Flow

    NASA Astrophysics Data System (ADS)

    Paganoni, M.; Foschi, M.; Cartwright, J. A.; Van Rensbergen, P.; Shipp, R. C.

    2015-12-01

    Bottom simulating reflectors (BSRs) are the primary indicators of the presence of gas hydrate systems and are generally considered to approximate the base of the gas hydrate stability zone. Here we use a combination of well-log, pressure-core, geochemical and high-resolution 3D seismic data, acquired in deepwater NW Borneo, to report the presence of gas hydrates both above and below a BSR at the top of a thrust-related anticline. This complex gas hydrate system overlies a conventional hydrocarbon reservoir. Hydrates beneath the BSR are interpreted to have a thermogenic origin because they contain significant quantities of C2+ hydrocarbons. The base of the hydrate stability coincides at the top of the anticline with a sudden decrease in resistivity in four adjacent wells. Away from the anticline top, in an environment dominated by mass-transport deposits, geochemical data from cores indicate a significant reduction in C2+ hydrocarbons. This change in gas composition is thought to reflect variations in hydrocarbon migration effectiveness and mechanisms. We demonstrate that, where thermogenic gases are efficiently transported to shallow parts of basins, hydrate stability zones could be much thicker than suggested by the depths of BSRs. This means that the carbon stored in thermogenic hydrate systems may be underestimated.

  4. Well log evaluation of natural gas hydrates

    SciTech Connect

    Collett, T.S.

    1992-10-01

    Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

  5. Well log evaluation of natural gas hydrates

    SciTech Connect

    Collett, T.S.

    1992-10-01

    Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence? Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

  6. Gas Hydrate Nucleation Processes

    NASA Astrophysics Data System (ADS)

    David, R. E.; Zatsepina, O.; Phelps, T. J.

    2003-12-01

    The onset of gas hydrate nucleation is greatly affected by the thermal history of the water that forms its lattice structure. Hydrate formation experiments were performed in a 72 liter pressure vessel by bubbling carbon dioxide through a 1 liter column at hydrate formation pressures (1.4 to 3.7 MPa) and temperatures (275.0 to 278.0 K) to quantify this effect. They show that when even a fraction ( e. g. 20 %) of the water in which hydrate has formed was recently frozen and thawed, the overpressurization for nucleation was reduced by an average of 50 % versus experiments performed in distilled water. In those experiments where a lower overpressure is present when hydrate nucleated, they tended to form on the surface of bubbles, whereas when a higher amount of overpressure was necessary for hydrate to nucleate, they appeared to form abruptly on bubble surfaces as well as from the bulk liquid phase. In approximation of classical nucleation, hydrate formation could be described as occurring by the spontaneous joining together of arising components of the hydrate lattice. In water that was frozen, and kept at a low temperature (< 275 K), molecular simulation models predict the predominance of water molecules organized as penatmeters, a possible subunit of the hydrate lattice. Our results suggest that in nature, initiation of hydrate formation may be strongly influenced by temperature dependant pre-structuring of water molecules prior to their contact with gas.

  7. Gas hydrates in the ocean environment

    USGS Publications Warehouse

    Dillon, William P.

    2002-01-01

    A GAS HYDRATE, also known as a gas clathrate, is a gas-bearing, icelike material. It occurs in abundance in marine sediments and stores immense amounts of methane, with major implications for future energy resources and global climate change. Furthermore, gas hydrate controls some of the physical properties of sedimentary deposits and thereby influences seafloor stability.

  8. Fundamentals and applications of gas hydrates.

    PubMed

    Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

    2011-01-01

    Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties.

  9. Resource Characterization and Quantification of Natural Gas-Hydrate and Associated Free-Gas Accumulations in the Prudhoe Bay - Kuparuk River Area on the North Slope of Alaska

    SciTech Connect

    Shirish Patil; Abhijit Dandekar

    2008-12-31

    Natural gas hydrates have long been considered a nuisance by the petroleum industry. Hydrates have been hazards to drilling crews, with blowouts a common occurrence if not properly accounted for in drilling plans. In gas pipelines, hydrates have formed plugs if gas was not properly dehydrated. Removing these plugs has been an expensive and time-consuming process. Recently, however, due to the geologic evidence indicating that in situ hydrates could potentially be a vast energy resource of the future, research efforts have been undertaken to explore how natural gas from hydrates might be produced. This study investigates the relative permeability of methane and brine in hydrate-bearing Alaska North Slope core samples. In February 2007, core samples were taken from the Mt. Elbert site situated between the Prudhoe Bay and Kuparuk oil fields on the Alaska North Slope. Core plugs from those core samples have been used as a platform to form hydrates and perform unsteady-steady-state displacement relative permeability experiments. The absolute permeability of Mt. Elbert core samples determined by Omni Labs was also validated as part of this study. Data taken with experimental apparatuses at the University of Alaska Fairbanks, ConocoPhillips laboratories at the Bartlesville Technology Center, and at the Arctic Slope Regional Corporation's facilities in Anchorage, Alaska, provided the basis for this study. This study finds that many difficulties inhibit the ability to obtain relative permeability data in porous media-containing hydrates. Difficulties include handling unconsolidated cores during initial core preparation work, forming hydrates in the core in such a way that promotes flow of both brine and methane, and obtaining simultaneous two-phase flow of brine and methane necessary to quantify relative permeability using unsteady-steady-state displacement methods.

  10. Thermal properties of methane gas hydrates

    USGS Publications Warehouse

    Waite, William F.

    2007-01-01

    Gas hydrates are crystalline solids in which molecules of a “guest” species occupy and stabilize cages formed by water molecules. Similar to ice in appearance (fig. 1), gas hydrates are stable at high pressures and temperatures above freezing (0°C). Methane is the most common naturally occurring hydrate guest species. Methane hydrates, also called simply “gas hydrates,” are extremely concentrated stores of methane and are found in shallow permafrost and continental margin sediments worldwide. Brought to sea-level conditions, methane hydrate breaks down and releases up to 160 times its own volume in methane gas. The methane stored in gas hydrates is of interest and concern to policy makers as a potential alternative energy resource and as a potent greenhouse gas that could be released from sediments to the atmosphere and ocean during global warming. In continental margin settings, methane release from gas hydrates also is a potential geohazard and could cause submarine landslides that endanger offshore infrastructure. Gas hydrate stability is sensitive to temperature changes. To understand methane release from gas hydrate, the U.S. Geological Survey (USGS) conducted a laboratory investigation of pure methane hydrate thermal properties at conditions relevant to accumulations of naturally occurring methane hydrate. Prior to this work, thermal properties for gas hydrates generally were measured on analog systems such as ice and non-methane hydrates or at temperatures below freezing; these conditions limit direct comparisons to methane hydrates in marine and permafrost sediment. Three thermal properties, defined succinctly by Briaud and Chaouch (1997), are estimated from the experiments described here: - Thermal conductivity, λ: if λ is high, heat travels easily through the material. - Thermal diffusivity, κ: if κ is high, it takes little time for the temperature to rise in the material. - Specific heat, cp: if cp is high, it takes a great deal of heat to

  11. Drilling and Production Testing the Methane Hydrate Resource Potential Associated with the Barrow Gas Fields

    SciTech Connect

    Steve McRae; Thomas Walsh; Michael Dunn; Michael Cook

    2010-02-22

    In November of 2008, the Department of Energy (DOE) and the North Slope Borough (NSB) committed funding to develop a drilling plan to test the presence of hydrates in the producing formation of at least one of the Barrow Gas Fields, and to develop a production surveillance plan to monitor the behavior of hydrates as dissociation occurs. This drilling and surveillance plan was supported by earlier studies in Phase 1 of the project, including hydrate stability zone modeling, material balance modeling, and full-field history-matched reservoir simulation, all of which support the presence of methane hydrate in association with the Barrow Gas Fields. This Phase 2 of the project, conducted over the past twelve months focused on selecting an optimal location for a hydrate test well; design of a logistics, drilling, completion and testing plan; and estimating costs for the activities. As originally proposed, the project was anticipated to benefit from industry activity in northwest Alaska, with opportunities to share equipment, personnel, services and mobilization and demobilization costs with one of the then-active exploration operators. The activity level dropped off, and this benefit evaporated, although plans for drilling of development wells in the BGF's matured, offering significant synergies and cost savings over a remote stand-alone drilling project. An optimal well location was chosen at the East Barrow No.18 well pad, and a vertical pilot/monitoring well and horizontal production test/surveillance well were engineered for drilling from this location. Both wells were designed with Distributed Temperature Survey (DTS) apparatus for monitoring of the hydrate-free gas interface. Once project scope was developed, a procurement process was implemented to engage the necessary service and equipment providers, and finalize project cost estimates. Based on cost proposals from vendors, total project estimated cost is $17.88 million dollars, inclusive of design work

  12. Gas hydrates: Technology status report

    SciTech Connect

    Not Available

    1987-01-01

    In 1983, the US Department of Energy (DOE) assumed the responsibility for expanding the knowledge base and for developing methods to recover gas from hydrates. These are ice-like mixtures of gas and water where gas molecules are trapped within a framework of water molecules. This research is part of the Unconventional Gas Recovery (UGR) program, a multidisciplinary effort that focuses on developing the technology to produce natural gas from resources that have been classified as unconventional because of their unique geologies and production mechanisms. Current work on gas hydrates emphasizes geological studies; characterization of the resource; and generic research, including modeling of reservoir conditions, production concepts, and predictive strategies for stimulated wells. Complementing this work is research on in situ detection of hydrates and field tests to verify extraction methods. Thus, current research will provide a comprehensive technology base from which estimates of reserve potential can be made, and from which industry can develop recovery strategies. 7 refs., 3 figs., 6 tabs.

  13. Physical Properties of Gas Hydrates: A Review

    DOE PAGES

    Gabitto, Jorge F.; Tsouris, Costas

    2010-01-01

    Memore » thane gas hydrates in sediments have been studied by several investigators as a possible future energy resource. Recent hydrate reserves have been estimated at approximately 10 16   m 3 of methane gas worldwide at standard temperature and pressure conditions. In situ dissociation of natural gas hydrate is necessary in order to commercially exploit the resource from the natural-gas-hydrate-bearing sediment. The presence of gas hydrates in sediments dramatically alters some of the normal physical properties of the sediment. These changes can be detected by field measurements and by down-hole logs. An understanding of the physical properties of hydrate-bearing sediments is necessary for interpretation of geophysical data collected in field settings, borehole, and slope stability analyses; reservoir simulation; and production models. This work reviews information available in literature related to the physical properties of sediments containing gas hydrates. A brief review of the physical properties of bulk gas hydrates is included. Detection methods, morphology, and relevant physical properties of gas-hydrate-bearing sediments are also discussed.« less

  14. Physical Properties of Gas Hydrates: A Review

    SciTech Connect

    Gabitto, Jorge; Tsouris, Costas

    2010-01-01

    Methane gas hydrates in sediments have been studied by several investigators as a possible future energy resource. Recent hydrate reserves have been estimated at approximately 1016?m3 of methane gas worldwide at standard temperature and pressure conditions. In situ dissociation of natural gas hydrate is necessary in order to commercially exploit the resource from the natural-gas-hydrate-bearing sediment. The presence of gas hydrates in sediments dramatically alters some of the normal physical properties of the sediment. These changes can be detected by field measurements and by down-hole logs. An understanding of the physical properties of hydrate-bearing sediments is necessary for interpretation of geophysical data collected in field settings, borehole, and slope stability analyses; reservoir simulation; and production models. This work reviews information available in literature related to the physical properties of sediments containing gas hydrates. A brief review of the physical properties of bulk gas hydrates is included. Detection methods, morphology, and relevant physical properties of gas-hydrate-bearing sediments are also discussed.

  15. Natural gas hydrate occurrence and issues

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1994-01-01

    Naturally occurring gas hydrate is found in sediment of two regions: (1) continental, including continental shelves, at high latitudes where surface temperatures are very cold, and (2) submarine outer continental margins where pressures are very high and bottom-water temperatures are near 0??C. Continental gas hydrate is found in association with onshore and offshore permafrost. Submarine gas hydrate is found in sediment of continental slopes and rises. The amount of methane present in gas hydrate is thought to be very large, but the estimates that have been made are more speculative than real. Nevertheless, at the present time there has been a convergence of ideas regarding the amount of methane in gas hydrate deposits worldwide at about 2 x 1016 m3 or 7 x 1017 ft3 = 7 x 105 Tcf [Tcf = trillion (1012) ft3]. The potentially large amount of methane in gas hydrate and the shallow depth of gas hydrate deposits are two of the principal factors driving research concerning this substance. Such a large amount of methane, if it could be commercially produced, provides a potential energy resource for the future. Because gas hydrate is metastable, changes of surface pressure and temperature affect its stability. Destabilized gas hydrate beneath the sea floor leads to geologic hazards such as submarine mass movements. Examples of submarine slope failures attributed to gas hydrate are found worldwide. The metastability of gas hydrate may also have an effect on climate. The release of methane, a 'greenhouse' gas, from destabilized gas hydrate may contribute to global warming and be a factor in global climate change.

  16. Study of Formation Mechanisms of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  17. Gas hydrates of outer continental margins

    SciTech Connect

    Kvenvolden, K.A. )

    1990-05-01

    Gas hydrates are crystalline substances in which a rigid framework of water molecules traps molecules of gas, mainly methane. Gas-hydrate deposits are common in continental margin sediment in all major oceans at water depths greater than about 300 m. Thirty-three localities with evidence for gas-hydrate occurrence have been described worldwide. The presence of these gas hydrates has been inferred mainly from anomalous lacoustic reflectors seen on marine seismic records. Naturally occurring marine gas hydrates have been sampled and analyzed at about tensites in several regions including continental slope and rise sediment of the eastern Pacific Ocean and the Gulf of Mexico. Except for some Gulf of Mexico gas hydrate occurrences, the analyzed gas hydrates are composed almost exclusively of microbial methane. Evidence for the microbial origin of methane in gas hydrates includes (1) the inverse relation between methane occurence and sulfate concentration in the sediment, (2) the subparallel depth trends in carbon isotopic compositions of methane and bicarbonate in the interstitial water, and (3) the general range of {sup 13}C depletion ({delta}{sub PDB}{sup 13}C = {minus}90 to {minus}60 {per thousand}) in the methane. Analyses of gas hydrates from the Peruvian outer continental margin in particular illustrate this evidence for microbially generated methane. The total amount of methane in gas hydrates of continental margins is not known, but estimates of about 10{sup 16} m{sup 3} seem reasonable. Although this amount of methane is large, it is not yet clear whether methane hydrates of outer continental margins will ever be a significant energy resource; however, these gas hydrates will probably constitute a drilling hazard when outer continental margins are explored in the future.

  18. Gas Hydrates Research Programs: An International Review

    SciTech Connect

    Jorge Gabitto; Maria Barrufet

    2009-12-09

    Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

  19. Tapping methane hydrates for unconventional natural gas

    USGS Publications Warehouse

    Ruppel, Carolyn

    2007-01-01

    Methane hydrate is an icelike form of concentrated methane and water found in the sediments of permafrost regions and marine continental margins at depths far shallower than conventional oil and gas. Despite their relative accessibility and widespread occurrence, methane hydrates have never been tapped to meet increasing global energy demands. With rising natural gas prices, production from these unconventional gas deposits is becoming economically viable, particularly in permafrost areas already being exploited for conventional oil and gas. This article provides an overview of gas hydrate occurrence, resource assessment, exploration, production technologies, renewability, and future challenges.

  20. Rapid gas hydrate formation process

    DOEpatents

    Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

    2013-01-15

    The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

  1. Toward production from gas hydrates: Current status, assessment of resources, and simulation-based evaluation of technology and potential

    USGS Publications Warehouse

    Moridis, G.J.; Collett, T.S.; Boswell, R.; Kurihara, M.; Reagan, M.T.; Koh, C.; Sloan, E.D.

    2009-01-01

    Gas hydrates (GHs) are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural GH accumulations, the status of the primary international research and development (R&D) programs, and the remaining science and technological challenges facing the commercialization of production. After a brief examination of GH accumulations that are well characterized and appear to be models for future development and gas production, we analyze the role of numerical simulation in the assessment of the hydrate-production potential, identify the data needs for reliable predictions, evaluate the status of knowledge with regard to these needs, discuss knowledge gaps and their impact, and reach the conclusion that the numerical-simulation capabilities are quite advanced and that the related gaps either are not significant or are being addressed. We review the current body of literature relevant to potential productivity from different types of GH deposits and determine that there are consistent indications of a large production potential at high rates across long periods from a wide variety of hydrate deposits. Finally, we identify (a) features, conditions, geology and techniques that are desirable in potential production targets; (b) methods to maximize production; and (c) some of the conditions and characteristics that render certain GH deposits undesirable for production. Copyright ?? 2009 Society of Petroleum Engineers.

  2. Gas hydrate cool storage system

    DOEpatents

    Ternes, M.P.; Kedl, R.J.

    1984-09-12

    The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

  3. Resource and hazard implications of gas hydrates in the Northern Gulf of Mexico: Results of the 2009 Joint Industry Project Leg II Drilling Expedition

    USGS Publications Warehouse

    Collett, Timothy S.; Boswell, Ray

    2012-01-01

    In the 1970's, Russian scientists were the first to suggest that gas hydrates, a crystalline solid of water and natural gas, and a historical curiosity to physical chemists, should occur in abundance in the natural environment. Since this early start, the scientific foundation has been built for the realization that gas hydrates are a global phenomenon, occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide. Recent field testing programs in the Arctic (Dallimore et al., 2008; Yamamoto and Dallimore, 2008) have indicated that natural gas can be produced from gas hydrate accumulations, particularly when housed in sand-rich sediments, with existing conventional oil and gas production technology (Collett et al., 2008) and preparations are now being made for the first marine field production tests (Masuda et al., 2009). Beyond a future energy resource, gas hydrates in some settings may represent a geohazard. Other studies also indicate that methane released to the atmosphere from destabilized gas hydrates may have contributed to global climate change in the past.

  4. Exploitation of subsea gas hydrate reservoirs

    NASA Astrophysics Data System (ADS)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2016-04-01

    Natural gas hydrates are considered to be a potential energy resource in the future. They occur in permafrost areas as well as in subsea sediments and are stable at high pressure and low temperature conditions. According to estimations the amount of carbon bonded in natural gas hydrates worldwide is two times larger than in all known conventional fossil fuels. Besides technical challenges that have to be overcome climate and safety issues have to be considered before a commercial exploitation of such unconventional reservoirs. The potential of producing natural gas from subsea gas hydrate deposits by various means (e.g. depressurization and/or injection of carbon dioxide) is numerically studied in the frame of the German research project »SUGAR«. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into a numerical model. The physics of the process leads to strong non-linear couplings between hydraulic fluid flow, hydrate dissociation and formation, hydraulic properties of the sediment, partial pressures and seawater solution of components and the thermal budget of the system described by the heat equation. This paper is intended to provide an overview of the recent development regarding the production of natural gas from subsea gas hydrate reservoirs. It aims at giving a broad insight into natural gas hydrates and covering relevant aspects of the exploitation process. It is focused on the thermodynamic principles and technological approaches for the exploitation. The effects occurring during natural gas production within hydrate filled sediment layers are identified and discussed by means of numerical simulation results. The behaviour of relevant process parameters such as pressure, temperature and phase saturations is described and compared for different strategies. The simulations are complemented by calculations for different safety relevant problems.

  5. Appraisal of gas hydrate resources based on a P- and S-impedance reflectivity template: case study from the deep sea sediments in Iran

    NASA Astrophysics Data System (ADS)

    Shoar, Behnam Hosseini; Javaherian, Abdolrahim; Keshavarz Farajkhah, Nasser; Seddigh Arabani, Mojtaba

    2013-12-01

    The occurrence of a bottom simulating reflector (BSR) in the 2D seismic data from Makran's accretionary prism reveals the presence of gas hydrate and free gas several hundred meters below the seafloor of Iran's deep sea. According to the global distribution of marine hydrates, they are widely present in deep sea sediments, where high operational costs and hazards cause a lack of well log information. Therefore, developing a method to quantify the hydrate resources with seismic data is an ultimate goal for unexplored regions. In this study, the so-called reflectivity templates (RTs) are introduced for quantification of the hydrate and free gas near the BSR. These RTs are intuitive crossplots of P-impedance and S-impedance contrasts across the BSR. They are calculated theoretically based on the effective medium theory for different hydrate distribution modes with some assumptions on porosity and mineralogical composition of unconsolidated sediments. This technique suggests the possibility of using the amplitude variation versus offset (AVO) analysis of the BSR for a quantitative interpretation when well log data are not available. By superimposing the AVO-derived P-impedance and S-impedance contrasts across the BSR on these RTs, the saturations of the hydrate and free gas near the BSR could be estimated. Validation of this approach by synthetic data showed that a reliable quantification could be achieved if the model parameters were rearranged to a form in which the AVO inversion was independent of the S-wave to P-wave velocity-ratio assumption. Based on this approach applied on the 2D marine pre-stack time migrated seismic line in offshore Iran, 4% to 28% of the gas hydrate and 1% to 2% of the free gas are expected to be accumulated near the thrusted-ridge and thrusted-footwall types of BSRs.

  6. Natural Gas Hydrates Update 1998-2000

    EIA Publications

    2001-01-01

    Significant events have transpired on the natural gas hydrate research and development front since "Future Supply Potential of Natural Gas Hydrates" appeared in Natural Gas 1998 Issues and Trends and in the Potential Gas Committee's 1998 biennial report.

  7. Spectroscopic methods in gas hydrate research.

    PubMed

    Rauh, Florian; Mizaikoff, Boris

    2012-01-01

    Gas hydrates are crystalline structures comprising a guest molecule surrounded by a water cage, and are particularly relevant due to their natural occurrence in the deep sea and in permafrost areas. Low molecular weight molecules such as methane and carbon dioxide can be sequestered into that cage at suitable temperatures and pressures, facilitating the transition to the solid phase. While the composition and structure of gas hydrates appear to be well understood, their formation and dissociation mechanisms, along with the dynamics and kinetics associated with those processes, remain ambiguous. In order to take advantage of gas hydrates as an energy resource (e.g., methane hydrate), as a sequestration matrix in (for example) CO(2) storage, or for chemical energy conservation/storage, a more detailed molecular level understanding of their formation and dissociation processes, as well as the chemical, physical, and biological parameters that affect these processes, is required. Spectroscopic techniques appear to be most suitable for analyzing the structures of gas hydrates (sometimes in situ), thus providing access to such information across the electromagnetic spectrum. A variety of spectroscopic methods are currently used in gas hydrate research to determine the composition, structure, cage occupancy, guest molecule position, and binding/formation/dissociation mechanisms of the hydrate. To date, the most commonly applied techniques are Raman spectroscopy and solid-state nuclear magnetic resonance (NMR) spectroscopy. Diffraction methods such as neutron and X-ray diffraction are used to determine gas hydrate structures, and to study lattice expansions. Furthermore, UV-vis spectroscopic techniques and scanning electron microscopy (SEM) have assisted in structural studies of gas hydrates. Most recently, waveguide-coupled mid-infrared spectroscopy in the 3-20 μm spectral range has demonstrated its value for in situ studies on the formation and dissociation of gas

  8. Gas Hydrate Storage of Natural Gas

    SciTech Connect

    Rudy Rogers; John Etheridge

    2006-03-31

    Environmental and economic benefits could accrue from a safe, above-ground, natural-gas storage process allowing electric power plants to utilize natural gas for peak load demands; numerous other applications of a gas storage process exist. A laboratory study conducted in 1999 to determine the feasibility of a gas-hydrates storage process looked promising. The subsequent scale-up of the process was designed to preserve important features of the laboratory apparatus: (1) symmetry of hydrate accumulation, (2) favorable surface area to volume ratio, (3) heat exchanger surfaces serving as hydrate adsorption surfaces, (4) refrigeration system to remove heat liberated from bulk hydrate formation, (5) rapid hydrate formation in a non-stirred system, (6) hydrate self-packing, and (7) heat-exchanger/adsorption plates serving dual purposes to add or extract energy for hydrate formation or decomposition. The hydrate formation/storage/decomposition Proof-of-Concept (POC) pressure vessel and supporting equipment were designed, constructed, and tested. This final report details the design of the scaled POC gas-hydrate storage process, some comments on its fabrication and installation, checkout of the equipment, procedures for conducting the experimental tests, and the test results. The design, construction, and installation of the equipment were on budget target, as was the tests that were subsequently conducted. The budget proposed was met. The primary goal of storing 5000-scf of natural gas in the gas hydrates was exceeded in the final test, as 5289-scf of gas storage was achieved in 54.33 hours. After this 54.33-hour period, as pressure in the formation vessel declined, additional gas went into the hydrates until equilibrium pressure/temperature was reached, so that ultimately more than the 5289-scf storage was achieved. The time required to store the 5000-scf (48.1 hours of operating time) was longer than designed. The lower gas hydrate formation rate is attributed to a

  9. Gas Hydrate and Pore Pressure

    NASA Astrophysics Data System (ADS)

    Tinivella, Umberta; Giustiniani, Michela

    2014-05-01

    Many efforts have been devoted to quantify excess pore pressures related to gas hydrate dissociation in marine sediments below the BSR using several approaches. Dissociation of gas hydrates in proximity of the BSR, in response to a change in the physical environment (i.e., temperature and/or pressure regime), can liberate excess gas incrising the local pore fluid pressure in the sediment, so decreasing the effective normal stress. So, gas hydrate dissociation may lead to excess pore pressure resulting in sediment deformation or failure, such as submarine landslides, sediment slumping, pockmarks and mud volcanoes, soft-sediment deformation and giant hummocks. Moreover, excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation, tectonic uplift, sea level fall, heating or inhibitor injection. In order to detect the presence of the overpressure below the BSR, we propose two approachs. The fist approach models the BSR depth versus pore pressure; in fact, if the free gas below the BSR is in overpressure condition, the base of the gas hydrate stability is deeper with respect to the hydrostatic case. This effect causes a discrepancy between seismic and theoretical BSR depths. The second approach models the velocities versus gas hydrate and free gas concentrations and pore pressure, considering the approximation of the Biot theory in case of low frequency, i.e. seismic frequency. Knowing the P and S seismic velocity from seismic data analysis, it is possibile to jointly estimate the gas hydrate and free gas concentrations and the pore pressure regime. Alternatively, if the S-wave velocity is not availbale (due to lack of OBS/OBC data), an AVO analysis can be performed in order to extract information about Poisson ratio. Our modeling suggests that the areas characterized by shallow waters (i.e., areas in which human infrastructures, such as pipelines, are present) are significantly affected by the presence of overpressure condition

  10. Methane hydrates and the future of natural gas

    USGS Publications Warehouse

    Ruppel, Carolyn

    2011-01-01

    For decades, gas hydrates have been discussed as a potential resource, particularly for countries with limited access to conventional hydrocarbons or a strategic interest in establishing alternative, unconventional gas reserves. Methane has never been produced from gas hydrates at a commercial scale and, barring major changes in the economics of natural gas supply and demand, commercial production at a large scale is considered unlikely to commence within the next 15 years. Given the overall uncertainty still associated with gas hydrates as a potential resource, they have not been included in the EPPA model in MITEI’s Future of Natural Gas report. Still, gas hydrates remain a potentially large methane resource and must necessarily be included in any consideration of the natural gas supply beyond two decades from now.

  11. Conditions for Fromation of Oceanic Natural Gas Hydrate Deposits

    NASA Astrophysics Data System (ADS)

    Max, M. M.

    2005-12-01

    Despite the widespread nature of oceanic natural gas hydrate and associated gas concentrations on continental margins, natural gas hydrate has yet to be proven to be an economically viable unconventional gas resource. In part, this is because unequivocal models for the formation of economic hydrate deposits do not yet exist and there is no exploration methodology for identifying the high-grade hydrate sweet spots that will constitute economic hydrate deposits. At this time, it appears that the most commercially viable high-grade hydrate deposits consist of naturally permeable strata that hosts a high proportion of solid hydrate filling of original porosity. The different means by which hydrate grows and the optimum conditions for the maintenance of a strong growth dynamic provide a key to predicting the location of potential hydrate deposits. Hydrate has been produced from natural seawater, which is a close approximation of connate water in marine sediments, and a variety of Hydrate Forming Gases (HFG) using several different types of crystallizers in laboratory experiments. The crystallizers have been developed to test a broad range of hydrate growth conditions by controlling pressure, temperature (or temperature gradients), and HFG saturation levels. Growth has been achieved in both aqueous and gaseous media. These results provide insight into formation of natural gas hydrate and may constrain the search for economic hydrate deposits Natural gas hydrate forms in one of three main growth modes in aqueous media; mineralizing solutions, diffusion in aqueous media, and solid diffusion. When the relative potential for growth of these modes are assessed along with geological and ground (pore) water provincing, the most likely locations within the gas hydrate stability zone (GHSZ) for recoverable hydrate natural gas deposits may be identified. The most rapid mode for growth of solid hydrate takes place on the seafloor in the presence of venting. Natural gas-rich fluids

  12. Simulation of subsea gas hydrate exploitation

    NASA Astrophysics Data System (ADS)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2014-05-01

    The recovery of methane from gas hydrate layers that have been detected in several subsea sediments and permafrost regions around the world is a promising perspective to overcome future shortages in natural gas supply. Being aware that conventional natural gas resources are limited, research is going on to develop technologies for the production of natural gas from such new sources. Thus various research programs have started since the early 1990s in Japan, USA, Canada, India, and Germany to investigate hydrate deposits and develop required technologies. In recent years, intensive research has focussed on the capture and storage of CO2 from combustion processes to reduce climate impact. While different natural or man-made reservoirs like deep aquifers, exhausted oil and gas deposits or other geological formations are considered to store gaseous or liquid CO2, the storage of CO2 as hydrate in former methane hydrate fields is another promising alternative. Due to beneficial stability conditions, methane recovery may be well combined with CO2 storage in the form of hydrates. Regarding technological implementation many problems have to be overcome. Especially mixing, heat and mass transfer in the reservoir are limiting factors causing very long process times. Within the scope of the German research project »SUGAR« different technological approaches for the optimized exploitation of gas hydrate deposits are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical processes are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs. Simulations based on geological field data have been carried out. The studies focus on the potential of gas production from turbidites and their fitness for CO2 storage. The effects occurring during gas production and CO2 storage within

  13. Well log evaluation of gas hydrate saturations

    USGS Publications Warehouse

    Collett, T.S.

    1998-01-01

    The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative due to the lack of previous quantitative studies. Gas volumes that may be attributed to a gas hydrate accumulation within a given geologic setting are dependent on a number of reservoir parameters; one of which, gas-hydrate saturation, can be assessed with data obtained from downhole well logging devices. The primary objective of this study was to develop quantitative well-log evaluation techniques which will permit the calculation of gas-hydrate saturations in gas-hydrate-bearing sedimentary units. The "standard" and "quick look" Archie relations (resistivity log data) yielded accurate gas-hydrate and free-gas saturations within all of the gas hydrate accumulations assessed in the field verification phase of the study. Compressional wave acoustic log data have been used along with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate accurate gas-hydrate saturations in all of the gas hydrate accumulations assessed in this study. The well log derived gas-hydrate saturations calculated in the field verification phase of this study, which range from as low as 2% to as high as 97%, confirm that gas hydrates represent a potentially important source of natural gas.

  14. [Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

    PubMed

    Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

    2015-11-01

    Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

  15. Gas hydrate reservoir characteristics and economics

    SciTech Connect

    Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.

    1992-06-01

    The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

  16. Gas hydrate reservoir characteristics and economics

    SciTech Connect

    Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.

    1992-01-01

    The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

  17. Marine electromagnetic methods for gas hydrate characterization

    NASA Astrophysics Data System (ADS)

    Weitemeyer, Karen Andrea

    Gas hydrate is a type of clathrate consisting of a gas molecule (usually methane) encased in a water lattice, and is found worldwide in marine and permafrost regions. Hydrate is important because it is a geo-hazard, has potential as an energy resource, and is a possible contributor to climate change. There are large uncertainties about the global amount of hydrate present, partly because the characterization of hydrate with seismic methods is unreliable. Marine electromagnetic (EM) methods can be used to image the bulk resistivity structure of the subsurface and are able to augment seismic data to provide valuable information about gas hydrate distribution in the marine environment. Marine controlled source electromagnetic (CSEM) sounding data from a pilot survey at Hydrate Ridge, located on the Cascadia subduction zone, show that regions with higher concentrations of hydrate are resistive. The apparent resistivities computed from the CSEM data are consistent for both apparent resistivity pseudosections and two-dimensional regularized inversion results. The 2D inversion results provide evidence of a strong resistor near the seismic bottom simulating reflector (BSR), and geologic structures are imaged to about a kilometer depth. Comparisons with electrical resistivity logging while drilling (LWD) data from Ocean Drilling Program Leg 204 show a general agreement except for one of three sites where the CSEM inversion shows a large resistor at depth as compared to the LWD. An overlay of the CSEM inversion with a collocated seismic line 230 from Trehu et al. (2001) exhibits remarkable similarities with the sedimentary layering, geologic structures, and the seismic BSR. Magnetotelluric (MT) sounding data collected simultaneously during the CSEM survey provide an electrical image of the oceanic crust and mantle (50 km depth) and the folding associated with the accretionary complex (top 2 km depth). In addition, the MT model provides a complementary low-resolution image of

  18. Interfacial phenomena in gas hydrate systems.

    PubMed

    Aman, Zachary M; Koh, Carolyn A

    2016-03-21

    Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries.

  19. Characterization of Gas-Hydrate Sediment: In Situ Evaluation of Hydrate Saturation in Pores of Pressured Sedimental Samples

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Konno, Y.; Kida, M.; Nagao, J.

    2014-12-01

    Hydrate saturation of gas-hydrate bearing sediment is a key of gas production from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Generally, hydrate saturations of sedimental samples are directly estimated by volume of gas generated from dissociation of gas hydrates in pore spaces, porosity data and volume of the sediments. Furthermore, hydrate saturation can be also assessed using velocity of P-wave through sedimental samples. Nevertheless, hydrate saturation would be changed by morphological variations (grain-coating, cementing and pore-filling model) of gas hydrates in pore spaces. Jin et al.[1,2] recently observed the O-H stretching bands of H2O molecules of methane hydrate in porous media using an attenuated total reflection IR (ATR-IR) spectra. They observed in situ hydrate formation/dissociation process in sandy samples (Tohoku Keisya number 8, grain size of ca. 110 μm). In this presentation, we present IR spectroscopy approach to in situ evaluation of hydrate saturation of pressured gas-hydrate sediments. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan. [1] Jin, Y.; Konno, Y.; Nagao, J. Energy Fules, 2012, 26, 2242-2247. [2] Jin, Y.; Oyama, H.; Nagao, J. Jpn. J. Appl. Phys. 2009, 48, No. 108001.

  20. Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: Constraints from ODP Leg 204

    USGS Publications Warehouse

    Trehu, A.M.; Long, P.E.; Torres, M.E.; Bohrmann, G.; Rack, F.R.; Collett, T.S.; Goldberg, D.S.; Milkov, A.V.; Riedel, M.; Schultheiss, P.; Bangs, N.L.; Barr, S.R.; Borowski, W.S.; Claypool, G.E.; Delwiche, M.E.; Dickens, G.R.; Gracia, E.; Guerin, G.; Holland, M.; Johnson, J.E.; Lee, Y.-J.; Liu, C.-S.; Su, X.; Teichert, B.; Tomaru, H.; Vanneste, M.; Watanabe, M. E.; Weinberger, J.L.

    2004-01-01

    Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space or 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally <2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ???10 m thick, and may occur in up to ???20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change. ?? 2004 Published by Elsevier B.V.

  1. Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204

    NASA Astrophysics Data System (ADS)

    Tréhu, A. M.; Long, P. E.; Torres, M. E.; Bohrmann, G.; Rack, F. R.; Collett, T. S.; Goldberg, D. S.; Milkov, A. V.; Riedel, M.; Schultheiss, P.; Bangs, N. L.; Barr, S. R.; Borowski, W. S.; Claypool, G. E.; Delwiche, M. E.; Dickens, G. R.; Gracia, E.; Guerin, G.; Holland, M.; Johnson, J. E.; Lee, Y.-J.; Liu, C.-S.; Su, X.; Teichert, B.; Tomaru, H.; Vanneste, M.; Watanabe, M.; Weinberger, J. L.

    2004-06-01

    Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space or 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally <2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ˜10 m thick, and may occur in up to ˜20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change.

  2. Natural gas hydrate in oceanic and permafrost environments

    USGS Publications Warehouse

    Max, Michael D.

    2003-01-01

    THE BEGINNINGS OF HYDRATE RESEARCH Until very recently, our understanding of hydrate in the natural environment and its impact on seafloor stability, its importance as a sequester of methane, and its potential as an important mechanism in the Earth's climate change system, was masked by our lack of appreciation of the vastness of the hydrate resource. Only a few publications on naturally occurring hydrate existed prior to 1975. The first published reference to oceanic gas hydrate (Bryan and Markl, 1966) and the first publication in the scientific literature (Stoll, et a1., 1971) show how recently it has been since the topic of naturally occurring hydrate has been raised. Recently, however, the number of hydrate publications has increased substantially, reflecting increased research into hydrate topics and the initiation of funding to support the researchers. Awareness of the existence of naturally occurring gas hydrate now has spread beyond the few scientific enthusiasts who pursued knowledge about the elusive hydrate because of simple interest and lurking suspicions that hydrate would prove to be an important topic. The first national conference on gas hydrate in the U.S. was held as recently as April, 1991 at the U.S. National Center of the U.s. Geological Survey in Reston Virginia (Max et al., 1991). The meeting was co-hosted by the U.s. Geological Survey, the Naval Research Laboratory, and the U.S.

  3. Well log evaluation of gas hydrate saturations

    USGS Publications Warehouse

    Collett, Timothy S.

    1998-01-01

    The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative due to the lack of previous quantitative studies. Gas volumes that may be attributed to a gas hydrate accumulation within a given geologic setting are dependent on a number of reservoir parameters; one of which, gas-hydrate saturation, can be assessed with data obtained from downhole well logging devices. The primary objective of this study was to develop quantitative well-log evaluation techniques which will permit the calculation of gas-hydrate saturations in gas-hydrate-bearing sedimentary units. The `standard' and `quick look' Archie relations (resistivity log data) yielded accurate gas-hydrate and free-gas saturations within all of the gas hydrate accumulations assessed in the field verification phase of the study. Compressional wave acoustic log data have been used along with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate accurate gas-hydrate saturations in this study. The well log derived gas-hydrate saturations calculated in the field verification phase of this study, which range from as low as 2% to as high as 97%, confirm that gas hydrates represent a potentially important source of natural gas.

  4. Microstructural characteristics of natural gas hydrates hosted in various sand sediments.

    PubMed

    Zhao, Jiafei; Yang, Lei; Liu, Yu; Song, Yongchen

    2015-09-21

    Natural gas hydrates have aroused worldwide interest due to their energy potential and possible impact on climate. The occurrence of natural gas hydrates hosted in the pores of sediments governs the seismic exploration, resource assessment, stability of deposits, and gas production from natural gas hydrate reserves. In order to investigate the microstructure of natural gas hydrates occurring in pores, natural gas hydrate-bearing sediments were visualized using microfocus X-ray computed tomography (CT). Various types of sands with different grain sizes and wettability were used to study the effect of porous materials on the occurrence of natural gas hydrates. Spatial distributions of methane gas, natural gas hydrates, water, and sands were directly identified. This work indicates that natural gas hydrates tend to reside mainly within pore spaces and do not come in contact with adjacent sands. Such an occurring model of natural gas hydrates is termed the floating model. Furthermore, natural gas hydrates were observed to nucleate at gas-water interfaces as lens-shaped clusters. Smaller sand grain sizes contribute to higher hydrate saturation. The wetting behavior of various sands had little effect on the occurrence of natural gas hydrates within pores. Additionally, geometric properties of the sediments were collected through CT image reconstructions. These findings will be instructive for understanding the microstructure of natural gas hydrates within major global reserves and for future resource utilization of natural gas hydrates.

  5. Well log characterization of natural gas hydrates

    USGS Publications Warehouse

    Collett, Timothy S.; Lee, Myung W.

    2011-01-01

    In the last 25 years we have seen significant advancements in the use of downhole well logging tools to acquire detailed information on the occurrence of gas hydrate in nature: From an early start of using wireline electrical resistivity and acoustic logs to identify gas hydrate occurrences in wells drilled in Arctic permafrost environments to today where wireline and advanced logging-while-drilling tools are routinely used to examine the petrophysical nature of gas hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. The most established and well known use of downhole log data in gas hydrate research is the use of electrical resistivity and acoustic velocity data (both compressional- and shear-wave data) to make estimates of gas hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. New downhole logging tools designed to make directionally oriented acoustic and propagation resistivity log measurements have provided the data needed to analyze the acoustic and electrical anisotropic properties of both highly inter-bedded and fracture dominated gas hydrate reservoirs. Advancements in nuclear-magnetic-resonance (NMR) logging and wireline formation testing have also allowed for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids (i.e., free-water along with clay and capillary bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms controlling the formation and occurrence of gas hydrate in nature along with data on gas hydrate reservoir properties (i.e., permeabilities) needed to accurately predict gas production rates for various gas hydrate

  6. Exploitation of marine gas hydrates: Benefits and risks (Invited)

    NASA Astrophysics Data System (ADS)

    Wallmann, K. J.

    2013-12-01

    Vast amounts of natural gas are stored in marine gas hydrates deposited at continental margins. The global inventory of carbon bound as methane in gas hydrates is currently estimated as 1000 × 500 Gt. Large-scale national research projects located mostly in South-East Asia but also in North America and Europe are aiming to exploit these ice-like solids as new unconventional resource of natural gas. Japan, South Korea and other Asian countries are taking the lead because their national waters harbor exploitable gas hydrate deposits which could be developed to reduce the dependency of these nations on costly LGN imports. In 2013, the first successful production test was performed off Japan at water depths of ca. 1000 m demonstrating that natural gas can be released and produced from marine hydrates by lowering the pressure in the sub-seabed hydrate reservoirs. In an alternative approach, CO2 from coal power plans and other industrial sources is used to release natural gas (methane) from hydrates while CO2 is bound and stored in the sub-surface as solid hydrate. These new approaches and technologies are still in an early pre-commercial phase; the costs of field development and gas production exceed the value of natural gas being produced from the slowly dissociating hydrates. However, new technologies are currently under development in the German SUGAR project and elsewhere to reduce costs and enhance gas production rates such that gas hydrates may become commercially exploitable over the coming decade(s). The exploitation of marine gas hydrates may help to reduce CO2 emissions from the fossil fuel sector if the produced natural gas is used to replace coal and/or LNG. Hydrate development could also provide important incentives for carbon capture technologies since CO2 can be used to produce natural gas from hydrates. However, leakage of gas may occur during the production process while slope failure may be induced by the accompanying dissociation/conversion of gas

  7. Gas hydrate cool storage system

    DOEpatents

    Ternes, Mark P.; Kedl, Robert J.

    1985-01-01

    This invention is a process for formation of a gas hydrate to be used as a cool storage medium using a refrigerant in water. Mixing of the immiscible refrigerant and water is effected by addition of a surfactant and agitation. The difficult problem of subcooling during the process is overcome by using the surfactant and agitation and performance of the process significantly improves and approaches ideal.

  8. A primer on the geological occurrence of gas hydrate

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1998-01-01

    This paper is part of the special publication Gas hydrates: relevance to world margin stability and climatic change (eds J.P. Henriet and J. Mienert).Natural gas hydrates occur world-wide in polar regions, usually associated with onshore and offshore permafrost, and in sediment of outer continental and insular margins. The total amount of methane in gas hydrates probably exceeds 1019 g of methane carbon. Three aspects of gas hydrates are important: their fossil fuel resource potential; their role as a submarine geohazard; and their effects on global climate change. Because gas hydrates represent a large amount of methane within 2000 m of the Earth's surface, they are considered to be an unconventional, unproven source of fossil fuel. Because gas hydrates are metastable, changes of pressure and temperature affect their stability. Destabilized gas hydrates beneath the sea floor lead to geological hazards such as submarine slumps and slides, examples of which are found world-wide. Destabilized gas hydrates may also affect climate through the release of methane, a 'greenhouse' gas, which may enhance global warming and be a factor in global climate change.

  9. Potential geologic hazards of Arctic gas hydrates

    SciTech Connect

    Collett, T.S. )

    1990-05-01

    Sediments of the Arctic region may contain enormous quantities of natural gas in the form of gas hydrates, which are crystalline substances composed of water and mostly methane gas. These ice-like substances are generally found in two distinct environments: (1) offshore in sediments of outer continental margins and (2) nearshore and onshore in areas associated with the occurrence of permafrost. Recently, US, Canadian, and Soviet researchers have described numerous drilling and production problems attributed to the presence of gas hydrates, including uncontrolled gas releases during drilling, collapsed casings, and gas leakage to the surface. When the drill bit penetrates a gas hydrate, the drilling mud, unless cooled significantly by the operator, will become highly gasified as the hydrate decomposes. The hydrate adjacent to the well bore will continue to decompose and gasify the drilling mud as long as drilling and/or production introduces heat into the hydrate-bearing interval. The production of hot fluids from depth through the permafrost and gas hydrate-bearing intervals adversely raises formation temperatures, thus decomposing the gas hydrates. If the disassociated, free gas is trapped behind the casing, reservoir pressures may substantially increase and cause the casing to collapse. In several wells in northern Alaska, the disassociated free gas has leaked to the surface outside the conductor casing. An additional drilling hazard associated with gas hydrates results from the sealing attributes of hydrates, which may trap large volumes of over pressured free gas at shallow depths. Even though documented problems attributed to the presence of gas hydrates have been relatively few, it is likely that as exploration and development activity moves farther offshore into deeper water (>300 m) and to higher latitudes in the Arctic, the frequency of gas hydrate-related problems will increase.

  10. Comparison of effective medium models for marine gas hydrate templates

    NASA Astrophysics Data System (ADS)

    Terry, D. A.; Knapp, C. C.; Knapp, J. H.

    2010-12-01

    Motivated by the value of marine gas hydrates as an energy resource and their potential influence on climate, we are engaged in a study to characterize gas hydrates in the Gulf of Mexico as part of the Gulf of Mexico Hydrates Research Consortium (GoM-HRC) at a research site on the continental margin. The locations of marine gas hydrates are commonly inferred by the presence of a distinctive Bottom Simulating Reflector (BSR) which typically marks the base of the gas hydrate stability zone (GHSZ) in seismic records. Yet lithology, as defined through sediment composition, grain size, particle shape, and fluid flow, is also critical in their emplacement and growth. Over more than thirty years, variations of Hertz-Mindlin type effective medium models have been developed for unconsolidated sediments. In the past few years improvements have been suggested to these models. This paper is directed at two objectives: 1) briefly review and consolidate the models, 2) apply and compare the models in context of rock physics templates for marine gas hydrates in unconsolidated, saturated sand and clay sediments. Here, we apply petroleum systems analysis to quantitatively estimate (and understand) the lithologic influence on gas hydrate seismic response. To do so, we are implementing recently developed rock physics models for saturated sediments with gas hydrates.

  11. Gas hydrate inhibition by perturbation of liquid water structure

    NASA Astrophysics Data System (ADS)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  12. Gas hydrate inhibition by perturbation of liquid water structure.

    PubMed

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-17

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  13. Potential effects of gas hydrate on human welfare.

    PubMed

    Kvenvolden, K A

    1999-03-30

    For almost 30 years. serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) submarine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a "greenhouse" gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected.

  14. Potential effects of gas hydrate on human welfare

    PubMed Central

    Kvenvolden, Keith A.

    1999-01-01

    For almost 30 years. serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) submarine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a “greenhouse” gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected. PMID:10097052

  15. Potential effects of gas hydrate on human welfare

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1999-01-01

    For almost 30 years, serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) sub-marine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a 'greenhouse' gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected.

  16. New Methods for Gas Hydrate Energy and Climate Studies

    NASA Astrophysics Data System (ADS)

    Ruppel, C. D.; Pohlman, J.; Waite, W. F.; Hunt, A. G.; Stern, L. A.; Casso, M.

    2015-12-01

    Over the past few years, the USGS Gas Hydrates Project has focused on advancements designed to enhance both energy resource and climate-hydrate interaction studies. On the energy side, the USGS now manages the Pressure Core Characterization Tools (PCCTs), which includes the Instrumented Pressure Testing Chamber (IPTC) that we have long maintained. These tools, originally built at Georgia Tech, are being used to analyze hydrate-bearing sediments recovered in pressure cores during gas hydrate drilling programs (e.g., Nankai 2012; India 2015). The USGS is now modifying the PCCTs for use on high-hydrate-saturation and sand-rich sediments and hopes to catalyze third-party tool development (e.g., visualization). The IPTC is also being used for experiments on sediments hosting synthetic methane hydrate, and our scanning electron microscope has recently been enhanced with a new cryo-stage for imaging hydrates. To support climate-hydrate interaction studies, the USGS has been re-assessing the amount of methane hydrate in permafrost-associated settings at high northern latitudes and examined the links between methane carbon emissions and gas hydrate dissociation. One approach relies on the noble gas signature of methane emissions. Hydrate dissociation uniquely releases noble gases partitioned by molecular weight, providing a potential fingerprint for hydrate-sourced methane emissions. In addition, we have linked a DOC analyzer with an IRMS at Woods Hole Oceanographic Institution, allowing rapid and precise measurement of DOC and DIC concentrations and carbon isotopic signatures. The USGS has also refined methods to measure real-time sea-air flux of methane and CO2 using cavity ring-down spectroscopy measurements coupled with other data. Acquiring ~8000 km of data on the Western Arctic, US Atlantic, and Svalbard margins, we have tested the Arctic methane catastrophe hypothesis and the link between seafloor methane emissions and sea-air methane flux.

  17. Handbook of gas hydrate properties and occurrence

    SciTech Connect

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  18. Detection and Appraisal of Gas Hydrates: Indian Scenario

    NASA Astrophysics Data System (ADS)

    Sain, K.

    2009-04-01

    Gas hydrates, found in shallow sediments of permafrost and outer continental margins, are crystalline form of methane and water. The carbon within global gas hydrates is estimated two times the carbon contained in world-wide fossil fuels. It is also predicted that 15% recovery of gas hydrates can meet the global energy requirement for the next 200 years. Several parameters like bathymetry, seafloor temperature, sediment thickness, rate of sedimentation and total organic carbon content indicate very good prospect of gas hydrates in the vast offshore regions of India. Methane stored in the form of gas hydrates within the Indian exclusive economic zone is estimated to be few hundred times the country's conventional gas reserve. India produces less than one-third of her oil requirement and gas hydrates provide great hopes as a viable source of energy in the 21st century. Thus identification and quantitative assessment of gas hydrates are very important. By scrutiny and reanalysis of available surface seismic data, signatures of gas hydrates have been found out in the Kerala-Konkan and Saurashtra basins in the western margin, and Krishna-Godavari, Mahanadi and Andaman regions in the eastern margin of India by mapping the bottom simulating reflector or BSR based on its characteristic features. In fact, the coring and drilling in 2006 by the Indian National Gas Hydrate Program have established the ground truth in the eastern margin. It has become all the more important now to identify further prospective regions with or without BSR; demarcate the lateral/areal extent of gas hydrate-bearing sediments and evaluate their resource potential in both margins of India. We have developed various approaches based on seismic traveltime tomography; waveform inversion; amplitude versus offset (AVO) modeling; AVO attributes; seismic attributes and rock physics modeling for the detection, delineation and quantification of gas-hydrates. The blanking, reflection strength, instantaneous

  19. NIST Gas Hydrate Research Database and Web Dissemination Channel

    PubMed Central

    Kroenlein, K.; Muzny, C. D.; Kazakov, A.; Diky, V. V.; Chirico, R. D.; Frenkel, M.; Sloan, E. D.

    2010-01-01

    To facilitate advances in application of technologies pertaining to gas hydrates, a freely available data resource containing experimentally derived information about those materials was developed. This work was performed by the Thermodynamic Research Center (TRC) paralleling a highly successful database of thermodynamic and transport properties of molecular pure compounds and their mixtures. Population of the gas-hydrates database required development of guided data capture (GDC) software designed to convert experimental data and metadata into a well organized electronic format, as well as a relational database schema to accommodate all types of numerical and metadata within the scope of the project. To guarantee utility for the broad gas hydrate research community, TRC worked closely with the Committee on Data for Science and Technology (CODATA) task group for Data on Natural Gas Hydrates, an international data sharing effort, in developing a gas hydrate markup language (GHML). The fruits of these efforts are disseminated through the NIST Sandard Reference Data Program [1] as the Clathrate Hydrate Physical Property Database (SRD #156). A web-based interface for this database, as well as scientific results from the Mallik 2002 Gas Hydrate Production Research Well Program [2], is deployed at http://gashydrates.nist.gov. PMID:27134781

  20. NIST Gas Hydrate Research Database and Web Dissemination Channel.

    PubMed

    Kroenlein, K; Muzny, C D; Kazakov, A; Diky, V V; Chirico, R D; Frenkel, M; Sloan, E D

    2010-01-01

    To facilitate advances in application of technologies pertaining to gas hydrates, a freely available data resource containing experimentally derived information about those materials was developed. This work was performed by the Thermodynamic Research Center (TRC) paralleling a highly successful database of thermodynamic and transport properties of molecular pure compounds and their mixtures. Population of the gas-hydrates database required development of guided data capture (GDC) software designed to convert experimental data and metadata into a well organized electronic format, as well as a relational database schema to accommodate all types of numerical and metadata within the scope of the project. To guarantee utility for the broad gas hydrate research community, TRC worked closely with the Committee on Data for Science and Technology (CODATA) task group for Data on Natural Gas Hydrates, an international data sharing effort, in developing a gas hydrate markup language (GHML). The fruits of these efforts are disseminated through the NIST Sandard Reference Data Program [1] as the Clathrate Hydrate Physical Property Database (SRD #156). A web-based interface for this database, as well as scientific results from the Mallik 2002 Gas Hydrate Production Research Well Program [2], is deployed at http://gashydrates.nist.gov.

  1. Gas hydrate detection and mapping on the US east coast

    SciTech Connect

    Ahlbrandt, T.S.; Dillon, W.P.

    1993-12-31

    Project objectives are to identify and map gas hydrate accumulations on the US eastern continental margin using remote sensing (seismic profiling) techniques and to relate these concentrations to the geological factors that-control them. In order to test the remote sensing methods, gas hydrate-cemented sediments will be tested in the laboratory and an effort will be made to perform similar physical tests on natural hydrate-cemented sediments from the study area. Gas hydrate potentially may represent a future major resource of energy. Furthermore, it may influence climate change because it forms a large reservoir for methane, which is a very effective greenhouse gas; its breakdown probably is a controlling factor for sea-floor landslides; and its presence has significant effect on the acoustic velocity of sea-floor sediments.

  2. Challenges, uncertainties and issues facing gas production from gas hydrate deposits

    SciTech Connect

    Moridis, G.J.; Collett, T.S.; Pooladi-Darvish, M.; Hancock, S.; Santamarina, C.; Boswell, R.; Kneafsey, T.; Rutqvist, J.; Kowalsky, M.; Reagan, M.T.; Sloan, E.D.; Sum, A.K.; Koh, C.

    2010-11-01

    The current paper complements the Moridis et al. (2009) review of the status of the effort toward commercial gas production from hydrates. We aim to describe the concept of the gas hydrate petroleum system, to discuss advances, requirement and suggested practices in gas hydrate (GH) prospecting and GH deposit characterization, and to review the associated technical, economic and environmental challenges and uncertainties, including: the accurate assessment of producible fractions of the GH resource, the development of methodologies for identifying suitable production targets, the sampling of hydrate-bearing sediments and sample analysis, the analysis and interpretation of geophysical surveys of GH reservoirs, well testing methods and interpretation of the results, geomechanical and reservoir/well stability concerns, well design, operation and installation, field operations and extending production beyond sand-dominated GH reservoirs, monitoring production and geomechanical stability, laboratory investigations, fundamental knowledge of hydrate behavior, the economics of commercial gas production from hydrates, and the associated environmental concerns.

  3. Exploration for Gas Hydrates in Deepwater Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Dai, J.; Dutta, N. C.

    2007-05-01

    In recent years, gas hydrates have drawn significant attention from scientific community worldwide due to their potential as an alternative energy resource and as a possible agent for both shallow drilling hazard, and global climate change. Gas hydrates have been known to exist extensively in shallow sediments from permafrost regions to deepwater oceans. The vast amount of naturally occurring hydrates is a large potential for an energy resource. While the world demand for fossil fuel is ever increasing and the supply is dwindling, it is imperative to assess whether gas hydrates can provide energy to fill the void. As a principle technology in hydrocarbon exploration, the seismic reflection method becomes a natural choice for exploring gas hydrates. In this paper, we present a petroleum systems approach to exploration of gas hydrates in which seismic data analysis and interpretation techniques play key roles. We developed an integrated, seismic-based, five-step workflow to delineate and quantify gas hydrates in the deepwater Gulf of Mexico (GoM). The method integrated geological interpretation, seismic processing and inversion, and rock physics modeling to ascertain the existence and quantify the naturally occurring gas hydrates. We applied the methodology on two blocks in the northern GoM and estimated hydrate concentration in the pore space, both at selected locations in 1D and a cube in 3D. Due to lack of hard data (well control) for the shallow seismic data, our predictions used analogue models based on geologic interpretation, seismic inversion, and the basic principles of rock physics. Based on model predictions, several wells were drilled recently on two blocks (KC 195 and ATV 14) in the GoM. We collected wireline, LWD/MWD, and core data. The post-drill analysis confirmed our methodology and validated the exploration mode. In this paper, we also present and discuss the drilling results and compare our pre-drill predictions with the drilling data and the

  4. In-situ characterization of gas hydrates

    NASA Astrophysics Data System (ADS)

    Moerz, T.; Brueckmann, W.; Linke, P.; Tuerkay, M.

    2003-04-01

    Gas hydrates are a dynamic reservoir in the marine carbon cycle and a periodically large and focussed source of methane probably constituting the largest carbon reservoir on earth. Therefore an important issue in gas hydrate research is the need for better tools to remotely estimate the volume and stability conditions of marine gas hydrate in the near sub-surface. It is also crucial to precisely determine the hydrate stability conditions in the near sub-surface, where gas hydrates are most susceptible to dissolution under changing P/T conditions. Our knowledge about the occurrence, spatial distribution, and life-cycle of gas hydrates in marine sediments is mainly derived from indirect geophysical and geochemical evidence. In a few instances gas hydrates have also been directly observed and sampled at the sea floor. For regional or global estimates of hydrate volumes and stability conditions however, new techniques for ground-truthing and calibration of geophysical, biological and geochemical methods are needed. During the OTEGA cruise with RV SONNE to Hydrate Ridge off Oregon a new device for in-situ characterization of gas hydrates was deployed and tested for the first time. The tool, HDSD (Hydrate Detection and Stability Determination) is being developed as part of Cooperative Research Center (SFB) 574 "Volatiles and Fluids in Subduction Zones". It is designed to identify and quantify small volumes of near-surface gas hydrate through continuous in-situ thermal and resistivity monitoring in a defined volume of sediment while it is slowly heated to destabilize gas hydrates embedded in it. In its current configuration HDSD is delivered to the seafloor by a video-guided GEOMAR BC Lander system. The sediment volume to be tested for the presence and abundance of gas hydrates is first isolated by a rectangular experiment chamber that is pushed into the upper 30cm of sediment. A "stinger", centrally mounted in the chamber and equipped with two arrays of sensors, provides

  5. Assessing the promise of natural gas hydrates as an unconventional source of energy

    NASA Astrophysics Data System (ADS)

    Collett, Timothy

    2007-03-01

    Gas hydrates are a naturally occurring ``ice-like'' combination of natural gas and water that have the potential to provide an immense resource of natural gas from the world's oceans and polar regions. The amount of natural gas contained in the world's gas hydrate accumulations is enormous, but these estimates are speculative and range over three orders-of-magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and technically recoverable undiscovered resources) for the world are estimated at approximately 440 trillion cubic meters as reported in the ``U.S. Geological Survey 2000 World Petroleum Assessment.'' Despite the enormous range in reported gas hydrate volumetric estimates, even the lowest reported estimates seem to indicate that gas hydrates are a much greater resource of natural gas than conventional accumulations. However, it is important to note that none of these assessments has predicted how much gas could actually be produced from the world's gas hydrate accumulations. Proposed methods of gas recovery from hydrates generally deal with dissociating or ``melting'' in-situ gas hydrates by heating the reservoir beyond the temperature of hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. Computer models have been developed to evaluate natural gas production from hydrates by both heating and depressurization. Depressurization is considered to be the most economically promising method for the production of natural gas from gas hydrates. Estimates vary on when gas hydrate production will play a significant role in the total world energy mix; however, it is possible that hydrates will be able to provide a sustainable supply of gas for the world's future energy needs.

  6. Towards a fundamental understanding of natural gas hydrates.

    PubMed

    Koh, Carolyn A

    2002-05-01

    Gas clathrate hydrates were first identified in 1810 by Sir Humphrey Davy. However, it is believed that other scientists, including Priestley, may have observed their existence before this date. They are solid crystalline inclusion compounds consisting of polyhedral water cavities which enclathrate small gas molecules. Natural gas hydrates are important industrially because the occurrence of these solids in subsea gas pipelines presents high economic loss and ecological risks, as well as potential safety hazards to exploration and transmission personnel. On the other hand, they also have technological importance in separation processes, fuel transportation and storage. They are also a potential fuel resource because natural deposits of predominantly methane hydrate are found in permafrost and continental margins. To progress with understanding and tackling some of the technological challenges relating to natural gas hydrate formation, inhibition and decomposition one needs to develop a fundamental understanding of the molecular mechanisms involved in these processes. This fundamental understanding is also important to the broader field of inclusion chemistry. The present article focuses on the application of a range of physico-chemical techniques and approaches for gaining a fundamental understanding of natural gas hydrate formation, decomposition and inhibition. This article is complementary to other reviews in this field, which have focused more on the applied, engineering and technological aspects of clathrate hydrates.

  7. Overview: Gas hydrate geology and geography

    SciTech Connect

    Malone, R.D.

    1993-01-01

    Several geological factors which are directly responsible for the presence or absence of gas hydrates have been reviewed and are: tectonic position of the region; sedimentary environments; structural deformation; shale diapirism; hydrocarbon generation and migration; thermal regime in the hydrate formation zone (HFZ); pressure conditions; and hydrocarbon gas supply to the HFZ. Work on gas hydrate formation in the geological environment has made significant advances, but there is still much to be learned. Work is continuing in the deeper offshore areas through the Ocean Drilling Program, Government Agencies, and Industry. The pressure/temperature conditions necessary for formation has been identified for various compositions of natural gas through laboratory investigations and conditions for formation are being advanced through drilling in areas where gas hydrates exist.

  8. Permafrost-associated natural gas hydrate occurrences on the Alaska North Slope

    USGS Publications Warehouse

    Collett, T.S.; Lee, M.W.; Agena, W.F.; Miller, J.J.; Lewis, K.A.; Zyrianova, M.V.; Boswell, R.; Inks, T.L.

    2011-01-01

    In the 1960s Russian scientists made what was then a bold assertion that gas hydrates should occur in abundance in nature. Since this early start, the scientific foundation has been built for the realization that gas hydrates are a global phenomenon, occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide. In 1995, the U.S. Geological Survey made the first systematic assessment of the in-place natural gas hydrate resources of the United States. That study suggested that the amount of gas in the gas hydrate accumulations of northern Alaska probably exceeds the volume of known conventional gas resources on the North Slope. Researchers have long speculated that gas hydrates could eventually become a producible energy resource, yet technical and economic hurdles have historically made gas hydrate development a distant goal. This view began to change in recent years with the realization that this unconventional resource could be developed with existing conventional oil and gas production technology. One of the most significant developments was the completion of the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope, which along with the Mallik project in Canada, have for the first time allowed the rational assessment of gas hydrate production technology and concepts. Almost 40 years of gas hydrate research in northern Alaska has confirmed the occurrence of at least two large gas hydrate accumulations on the North Slope. We have also seen in Alaska the first ever assessment of how much gas could be technically recovered from gas hydrates. However, significant technical concerns need to be further resolved in order to assess the ultimate impact of gas hydrate energy resource development in northern Alaska. ?? 2009 Elsevier Ltd.

  9. Reservoir controls on the occurrence and production of gas hydrates in nature

    USGS Publications Warehouse

    Collett, Timothy Scott

    2014-01-01

    modeling has shown that concentrated gas hydrate occurrences in sand reservoirs are conducive to existing well-based production technologies. The resource potential of gas hydrate accumulations in sand-dominated reservoirs have been assessed for several polar terrestrial basins. In 1995, the U.S. Geological Survey (USGS) assigned an in-place resource of 16.7 trillion cubic meters of gas for hydrates in sand-dominated reservoirs on the Alaska North Slope. In a more recent assessment, the USGS indicated that there are about 2.42 trillion cubic meters of technically recoverable gas resources within concentrated, sand-dominated, gas hydrate accumulations in northern Alaska. Estimates of the amount of in-place gas in the sand dominated gas hydrate accumulations of the Mackenzie Delta Beaufort Sea region of the Canadian arctic range from 1.0 to 10 trillion cubic meters of gas. Another prospective gas hydrate resources are those of moderate-to-high concentrations within sandstone reservoirs in marine environments. In 2008, the Bureau of Ocean Energy Management estimated that the Gulf of Mexico contains about 190 trillion cubic meters of gas in highly concentrated hydrate accumulations within sand reservoirs. In 2008, the Japan Oil, Gas and Metals National Corporation reported on a resource assessment of gas hydrates in which they estimated that the volume of gas within the hydrates of the eastern Nankai Trough at about 1.1 trillion cubic meters, with about half concentrated in sand reservoirs. Because conventional production technologies favor sand-dominated gas hydrate reservoirs, sand reservoirs are considered to be the most viable economic target for gas hydrate production and will be the prime focus of most future gas hydrate exploration and development projects.

  10. Measuring In situ Dissolved Methane Concentrations in Gas Hydrate-Rich Systems. Part 2: Investigating Mechanisms Controlling Hydrate Dissolution

    NASA Astrophysics Data System (ADS)

    Wilson, R. M.; Lapham, L.; Riedel, M.; Chanton, J.

    2010-12-01

    Methane is a potent greenhouse gas, twenty times more infrared-active than CO2, and an important energy source. For these reasons, methane hydrate, one of the largest potential reservoirs of methane on earth, is of considerable interest to scientists and industry alike. In particular, questions relating to the stability of methane hydrate are becoming more important as concern about the release of methane into overlying ocean (and eventually the atmosphere) and interest in the recovery of methane from this resource increase. Three primary factors control hydrate stability: pressure (P), temperature (T), and the gas concentration in the surrounding environment. Pressure and temperature govern the stability of the hydrate structure. When hydrate is exposed to P/T regimes outside of the stability zone (HSZ), the hydrate decomposes by dissociation, a relatively fast process resulting in the release of gaseous phase methane (CH4(g)). However, if the P/T regime is within the HSZ, but the concentration of the guest gas (typically CH4) in the surroundings is below saturation, the hydrate will decompose by dissolution resulting in a phase change between hydrate and the dissolved gas phase (CH4(aq)). OsmoSamplers were deployed at a methane hydrate outcrop in Barkley Canyon, Northern Cascadia Margin, collecting porewater samples in a gradient at 1cm increments away from the hydrate surface. Methane, ethane, and propane concentrations in the porewater samples were measured at 6-day resolution over a period of 9 months. At three centimeters from the hydrate face, methane concentrations were significantly lower than predicted saturation for conditions at this site. Curiously, in situ observations of natural hydrate dissolution are up to two orders of magnitude lower than predicted diffusion-controlled dissolution based on surrounding methane concentrations. Since diffusion of methane away from the hydrate surface has been implicated as the dominant control of hydrate dissolution

  11. Gas Hydrates: From Laboratory Curiosity to Potential Global Powerhouse

    NASA Astrophysics Data System (ADS)

    Pellenbarg, Robert E.; Max, Michael D.

    2001-07-01

    Clathrates are a nonstoichiometric class of compounds that consist of a three-dimensional host molecule lattice and voids in the lattice that can be occupied by guest molecules, particularly common gases (e.g. methane, CH4). Where the host crystal structure is water the clathrate is termed a hydrate; these are the focus of increasing research. Methane (natural gas) hydrates are now recognized to occur in huge volumes in deep marine sediments and permafrost. These naturally occurring hydrates may constitute the next major energy resource of the planet and could provide the basis for the transition from our present petroleum economy to one based on methane.

  12. Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204

    SciTech Connect

    Trehu, Ann M.; Long, Philip E.; Torres, M E.; Bohrmann, G; Rack, F R.; Collett, T S.; Goldberg, D S.; Milkov, A V.; Riedel, M; Schultheiss, P; Bangs, N L.; Barr, S R.; Borowski, W S.; Claypool, G E.; Delwiche, Mark E.; Dickens, G R.; Gracia, E; Guerin, G; Holland, M; Johnson, Jerry E.; Lee, Y J.; Liu, C S.; Su, X; Teichert, B; Tomaru, H; Vanneste, M; Watanabe, M; Weinberger, Jill L.

    2004-03-01

    Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, the entire gas hydrate stability zone was sampled in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space of 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs.

  13. ConocoPhillips Gas Hydrate Production Test

    SciTech Connect

    Schoderbek, David; Farrell, Helen; Howard, James; Raterman, Kevin; Silpngarmlert, Suntichai; Martin, Kenneth; Smith, Bruce; Klein, Perry

    2013-06-30

    Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

  14. Hydrate Control for Gas Storage Operations

    SciTech Connect

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  15. Indian National Gas Hydrate Program Expedition 01 report

    USGS Publications Warehouse

    Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.; ,

    2015-01-01

    The Indian National Gas Hydrate Program Expedition 01 was designed to study the gas-hydrate occurrences off the Indian Peninsula and along the Andaman convergent margin with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. During Indian National Gas Hydrate Program Expedition 01, dedicated gas-hydrate coring, drilling, and downhole logging operations were conducted from 28 April 2006 to 19 August 2006.

  16. Painting a Picture of Gas Hydrate Distribution with Thermal Images

    SciTech Connect

    Weinberger, Jill L.; Brown, Kevin M.; Long, Philip E.

    2005-02-25

    Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, the entire gas hydrate stability zone was sampled in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space of 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs.

  17. Gas hydrates: past and future geohazard?

    PubMed

    Maslin, Mark; Owen, Matthew; Betts, Richard; Day, Simon; Dunkley Jones, Tom; Ridgwell, Andrew

    2010-05-28

    Gas hydrates are ice-like deposits containing a mixture of water and gas; the most common gas is methane. Gas hydrates are stable under high pressures and relatively low temperatures and are found underneath the oceans and in permafrost regions. Estimates range from 500 to 10,000 giga tonnes of carbon (best current estimate 1600-2000 GtC) stored in ocean sediments and 400 GtC in Arctic permafrost. Gas hydrates may pose a serious geohazard in the near future owing to the adverse effects of global warming on the stability of gas hydrate deposits both in ocean sediments and in permafrost. It is still unknown whether future ocean warming could lead to significant methane release, as thermal penetration of marine sediments to the clathrate-gas interface could be slow enough to allow a new equilibrium to occur without any gas escaping. Even if methane gas does escape, it is still unclear how much of this could be oxidized in the overlying ocean. Models of the global inventory of hydrates and trapped methane bubbles suggest that a global 3( degrees )C warming could release between 35 and 940 GtC, which could add up to an additional 0.5( degrees )C to global warming. The destabilization of gas hydrate reserves in permafrost areas is more certain as climate models predict that high-latitude regions will be disproportionately affected by global warming with temperature increases of over 12( degrees )C predicted for much of North America and Northern Asia. Our current estimates of gas hydrate storage in the Arctic region are, however, extremely poor and non-existent for Antarctica. The shrinking of both the Greenland and Antarctic ice sheets in response to regional warming may also lead to destabilization of gas hydrates. As ice sheets shrink, the weight removed allows the coastal region and adjacent continental slope to rise through isostacy. This removal of hydrostatic pressure could destabilize gas hydrates, leading to massive slope failure, and may increase the risk of

  18. Gas Hydrate Research Site Selection and Operational Research Plans

    NASA Astrophysics Data System (ADS)

    Collett, T. S.; Boswell, R. M.

    2009-12-01

    In recent years it has become generally accepted that gas hydrates represent a potential important future energy resource, a significant drilling and production hazard, a potential contributor to global climate change, and a controlling factor in seafloor stability and landslides. Research drilling and coring programs carried out by the Ocean Drilling Program (ODP), the Integrated Ocean Drilling Program (IODP), government agencies, and several consortia have contributed greatly to our understanding of the geologic controls on the occurrence of gas hydrates in marine and permafrost environments. For the most part, each of these field projects were built on the lessons learned from the projects that have gone before them. One of the most important factors contributing to the success of some of the more notable gas hydrate field projects has been the close alignment of project goals with the processes used to select the drill sites and to develop the project’s operational research plans. For example, IODP Expedition 311 used a transect approach to successfully constrain the overall occurrence of gas hydrate within the range of geologic environments within a marine accretionary complex. Earlier gas hydrate research drilling, including IODP Leg 164, were designed primarily to assess the occurrence and nature of marine gas hydrate systems, and relied largely on the presence of anomalous seismic features, including bottom-simulating reflectors and “blanking zones”. While these projects were extremely successful, expeditions today are being increasingly mounted with the primary goal of prospecting for potential gas hydrate production targets, and site selection processes designed to specifically seek out anomalously high-concentrations of gas hydrate are needed. This approach was best demonstrated in a recently completed energy resource focused project, the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II (GOM JIP Leg II), which featured the collection of a

  19. Gas origin of hydrate in the Qilian Mountain permafrost, Qinghai

    NASA Astrophysics Data System (ADS)

    Lu, Z.; Zhu, Y.; Liu, H.; Zhang, Y.; Sun, Z.

    2012-12-01

    Gas origin of hydrate is not clear yet in the Muli of Qilian mountain permafrost, which will obviously affect its further exploration direction. A case is illustrated in the hole of DK-2 during gas hydrate drilling; gas composition and isotopes of gas hydrate and its associated gases are analyzed; organic geochemistry on mudstone, oily shale, coal, oil & gas indications are correlated within the interval of gas hydrate occurrences; the aim is to discuss the source of gases from gas hydrate and its implication to gas hydrate exploration in the study area. Results from gas composition and isotopes of gas hydrate and its associated gases reveal that the origin of gases from gas hydrate is mainly concomitant with deep oil or crude oil in the study area. Parameters for the abundance, type and thermal evolution of organic matter in mudstone, oil shale, coal in the same interval of gas hydrate occurrence suggest that these strata, especially within gas hydrate stability zone, play little role in gas sources for gas hydrate. Reservoir pyrolysis results for oil & gas indication-bearing cores reveal that oil & gas indications are closely associated with gas hydrate within its interval, indicating that they may serve as a sign of gas hydrate in the study area.

  20. Natural and synthetic gas hydrates studied by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Savy, Jean-Philippe; Bigalke, Nikolaus; Aloisi, Giovanni; Kossel, Elke; Pansegrau, Moritz; Haeckel, Matthias

    2010-05-01

    Over the past decade, the interest in using CH4-hydrates as an energy resource and CO2-hydrates as a storage option for anthropogenic CO2 has grown in the scientific community as well as in the oil and gas industry. Among all the techniques used to characterize gas hydrates, the non-destructive, non-invasive Raman spectroscopy provides significant insights into the structure and composition of hydrates. In this study, we compare gas hydrates synthetically produced in the laboratory with natural hydrate samples collected from marine sediments. CO2 and CH4 gas hydrates were investigated with a high-resolution Raman microscope at in-situ p-T conditions. A water-filled glass capillary (inner diameter: 1.7 mm) was placed in a stainless steel cell, which was sealed, cooled down to 3.6 ° C and pressurized to 60 bar with liquid CO2. Video images taken after 1 h revealed droplets (~10 μm in diameter) trapped in the ice-like solid. The two Fermi dyads of CO2 in the liquid and hydrate phase at 1274 & 1381 cm1 and 1280 & 1384 cm-1, respectively, confirm the presence of liquid CO2 droplets trapped in a CO2-hydrate matrix. Equivalent experiments were conducted with CH4 gas at 1 ° C and 90 bar. The nucleation of CH4-hydrate was followed in the Raman spectral region of the C-H stretching mode. At the early stage of the nucleation, the peak at 2915 cm-1 (CH4 in small cages) was stronger than the one at 2904 cm-1 (CH4 in large cages) indicating that methane starts to populate the small 512 cages of the s-I hydrate structure first and then, as nucleation continues, the large cages are stabilized leading to a quickly growing peak at 2904 cm-1 until a final peak intensity ratio of 3.7 is established. In contrast to other studies, intermediate stabilization of the s-II structure was not observed. Video images confirmed the absence of gas inclusions. The hydrate density, 1.1 & 0.9 for CO2-hydrate and CH4-hydrate respectively, compared to the one of water may explain the formation of

  1. Apparatus investigates geological aspects of gas hydrates

    USGS Publications Warehouse

    Booth, J.S.; Winters, W.J.; Dillon, William P.

    1999-01-01

    The US Geological Survey has developed a laboratory research system which allows the study of the creation and dissociation of gas hydrates under deepwater conditions and with different sediment types and pore fluids. The system called GHASTLI (gas hydrate and sediment test laboratory instrument) comprises a pressure chamber which holds a sediment specimen, and which can simulate water depths to 2,500m and different sediment overburden. Seawater and gas flow through a sediment specimen can be precisely controlled and monitored. It can simulate a wide range of geology and processes and help to improve understanding of gas hydrate processes and aid prediction of geohazards, their control and potential use as an energy source. This article describes GHASTLI and how it is able to simulate natural conditions, focusing on fluid volume, acoustic velocity-compressional and shear wave, electric resistance, temperature, pore pressure, shear strength, and permeability.

  2. Controls on Gas Hydrate Formation and Dissociation

    SciTech Connect

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  3. Integrated Geologic and Geophysical Assessment of the Eileen Gas Hydrate Accumulation, North Slope, Alaska

    SciTech Connect

    Timothy S. Collett; David J. Taylor; Warren F. Agena; Myung W. Lee; John J. Miller; Margarita Zyrianova

    2005-04-30

    Using detailed analysis and interpretation of 2-D and 3-D seismic data, along with modeling and correlation of specially processed log data, a viable methodology has been developed for identifying sub-permafrost gas hydrate prospects within the Gas Hydrate Stability Zone (HSZ) and associated ''sub-hydrate'' free gas prospects in the Milne Point area of northern Alaska (Figure 1). The seismic data, in conjunction with modeling results from a related study, was used to characterize the conditions under which gas hydrate prospects can be delineated using conventional seismic data, and to analyze reservoir fluid properties. Monte Carlo style gas hydrate volumetric estimates using Crystal Ball{trademark} software to estimate expected in-place reserves shows that the identified prospects have considerable potential as gas resources. Future exploratory drilling in the Milne Point area should provide answers about the producibility of these shallow gas hydrates.

  4. Gas in Place Resource Assessment for Concentrated Hydrate Deposits in the Kumano Forearc Basin, Offshore Japan, from NanTroSEIZE and 3D Seismic Data

    NASA Astrophysics Data System (ADS)

    Taladay, K.; Boston, B.

    2015-12-01

    Natural gas hydrates (NGHs) are crystalline inclusion compounds that form within the pore spaces of marine sediments along continental margins worldwide. It has been proposed that these NGH deposits are the largest dynamic reservoir of organic carbon on this planet, yet global estimates for the amount of gas in place (GIP) range across several orders of magnitude. Thus there is a tremendous need for climate scientists and countries seeking energy security to better constrain the amount of GIP locked up in NGHs through the development of rigorous exploration strategies and standardized reservoir characterization methods. This research utilizes NanTroSEIZE drilling data from International Ocean Drilling Program (IODP) Sites C0002 and C0009 to constrain 3D seismic interpretations of the gas hydrate petroleum system in the Kumano Forearc Basin. We investigate the gas source, fluid migration mechanisms and pathways, and the 3D distribution of prospective HCZs. There is empirical and interpretive evidence that deeply sourced fluids charge concentrated NGH deposits just above the base of gas hydrate stability (BGHS) appearing in the seismic data as continuous bottoms simulating reflections (BSRs). These HCZs cover an area of 11 by 18 km, range in thickness between 10 - 80 m with an average thickness of 40 m, and are analogous to the confirmed HCZs at Daini Atsumi Knoll in the eastern Nankai Trough where the first offshore NGH production trial was conducted in 2013. For consistency, we calculated a volumetric GIP estimate using the same method employed by Japan Oil, Gas and Metals National Corporation (JOGMEC) to estimate GIP in the eastern Nankai Trough. Double BSRs are also common throughout the basin, and BGHS modeling along with drilling indicators for gas hydrates beneath the primary BSRs provides compelling evidence that the double BSRs reflect a BGHS for structure-II methane-ethane hydrates beneath a structure-I methane hydrate phase boundary. Additional drilling

  5. Sedimentological properties of hydrate-bearing sediments and their relation to gas hydrate saturation in the eastern Nankai Trough

    NASA Astrophysics Data System (ADS)

    Ito, T.; Komatsu, Y.; Fujii, T.; Suzuki, K.; Nakatsuka, Y.; Egawa, K.; Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Minagawa, H.; Nagao, J.

    2013-12-01

    This study presents details of the sedimentological features such as core lithologies and particle size distributions, and their relation to gas hydrate saturation of the eastern Nankai Trough sediments. During the 2012 JOGMEC/JAPEX Pressure coring operation at the eastern Nankai Trough offshore Japan, one site was drilled and a gas hydrate-bearing sediment core in the gas hydrate stability zone above the seismic bottom-simulating reflector (BRS) was recovered by pressure coring successfully. The gas hydrate-bearing sediment core mainly consists of channel-fill turbidite sand, repeated turbidite sequences with hemipelagic mud, and hemipelagic mud from bottom to top of the core. It has been reported that gas hydrate is preferentially accumulated in certain types of sediments, for example in coarse-grained turbidite sands and in diatomaceous silty sediments with low capillary force. This fact suggests that sediment composition also plays an essential role of gas hydrate saturation in addition to particle size. According to the sediments from the eastern Nankai Trough, the distributions of coarse-grained turbidite sands appear to be one of the most important factors controlling the natural gas hydrate occurrences owing to no significant sediment composition changes. The eastern Nankai Trough sediment can thus be appropriate material for evaluating particle size effects on gas hydrate saturation in natural sediments. The stratigraphic profiles of sedimentological features imply that the median size and sorting of the host sediment are key sediment properties to control the stratigraphic gas hydrate saturation in channel-fill turbidite sand and repeated turbidite sequences with hemipelagic mud. This study is financially supported by the Research Consortium for Methane Hydrate Resources in Japan (the MH21 Research Consortium).

  6. Hydrated metal ions in the gas phase.

    PubMed

    Beyer, Martin K

    2007-01-01

    Studying metal ion solvation, especially hydration, in the gas phase has developed into a field that is dominated by a tight interaction between experiment and theory. Since the studied species carry charge, mass spectrometry is an indispensable tool in all experiments. Whereas gas-phase coordination chemistry and reactions of bare metal ions are reasonably well understood, systems containing a larger number of solvent molecules are still difficult to understand. This review focuses on the rich chemistry of hydrated metal ions in the gas phase, covering coordination chemistry, charge separation in multiply charged systems, as well as intracluster and ion-molecule reactions. Key ideas of metal ion solvation in the gas phase are illustrated with rare-gas solvated metal ions.

  7. Micro structure of gas-hydrate sediment: in situ sub-sampling from pressured sedimental samples

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Konno, Y.; Yoneda, J.; Egawa, K.; Kida, M.; Ito, T.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

    2013-12-01

    Porosity of gas-hydrate bearing sediment is a key of gas production efficient from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Because in situ evaluation of porosity with hydrate in pores is difficult, porosity values were discussed from hydrate bearing sediment quenched by liquid nitrogen. In the case of quenched sample, sand matrix in GH sediments could have been changed by freezing water in pores. Therefore, porosity data in previous reports may be over estimated comparing with nature of sediments at in situ condition. We developed in situ sub-sampling system for pressured natural gas-hydrate sediments. A small sedimental piece can be sampled from pressured gas hydrate sediments without pressure-release to atmosphere by using the our developed apparatus. In this presentation, we demonstrated sub-sampling from an artificial gas-hydrate sediment and measured micro-scale structure of the sub-sampled gas-hydrate sedimental piece. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.

  8. Three dimensional thermobaric modeling of a gas hydrate system

    NASA Astrophysics Data System (ADS)

    Williams, Amanda Quigley

    Seismic imaging is recognized as the most cost effective method for identifying the presence of gas hydrate resources. The base of the gas hydrate stability zone is recognized by the presence of regionally extensive bottom simulating reflectors (BSR). However, in some areas such as the Gulf of Mexico, regionally extensive BSRs are not found. In such cases, an understanding of the thermobaric conditions may be used to determine the location of gas hydrates and the base of the gas hydrate stability zone. The aim of this research is to combine seismic velocity analysis and thermal modeling to predict the base of the hydrate stability zone. As a case study, we apply this modeling to the extensively documented site at Woolsey Mound, MC-118, Gulf of Mexico. Woolsey Mound, and much of the Gulf of Mexico, has been greatly affected by salt tectonics. Multiple seismic and CHIRP surveys have been collected at Woolsey Mound, but the base of the gas hydrate stability zone has been elusive due to the complexities associated with the presence of salt. The velocity analysis and previous studies on the sedimentary environment were the basis to derive the thermal and salinity conditions. Data from the heat flow survey provide an upper boundary condition at the sea floor in order to create a more accurate thermal model; the velocity model helped accurately place the salt diapir within the mound system. Hydrate phase equilibrium models were used to estimate a thermobaric model for Woolsey Mound. Using two different salinity gradients, the base of the gas hydrate stability zone was found to be located within 70 m of the seafloor with a salt concentration up to 90% at the shallowest point of the salt diapir, and 120 m of the seafloor with a salt concentration up to standard temperature and pressure conditions of salt (of approximately 56%) at the shallowest point of the salt diapir. This study provides a preliminary look at how the temperature and salinity affect the depth at which gas

  9. The Research Path to Determining the Natural Gas Supply Potential of Marine Gas Hydrates

    SciTech Connect

    Boswell, R.M.; Rose, K.K.; Baker, R.C.

    2008-06-01

    A primary goal of the U.S. National Interagency Gas Hydrates R&D program is to determine the natural gas production potential of marine gas hydrates. In pursuing this goal, four primary areas of effort are being conducted in parallel. First, are wide-ranging basic scientific investigations in both the laboratory and in the field designed to advance the understanding of the nature and behavior of gas hydrate bearing sediments (GHBS). This multi-disciplinary work has wide-ranging direct applications to resource recovery, including assisting the development of exploration and production technologies through better rock physics models for GHBS and also in providing key data for numerical simulations of productivity, reservoir geomechanical response, and other phenomena. In addition, fundamental science efforts are essential to developing a fuller understanding of the role gas hydrates play in the natural environment and the potential environmental implications of gas hydrate production, a critical precursor to commercial extraction. A second area of effort is the confirmation of resource presence and viability via a series of multi-well marine drilling expeditions. The collection of data in the field is essential to further clarifying what proportion of the likely immense in-place marine gas hydrate resource exists in accumulations of sufficient quality to represent potential commercial production prospects. A third research focus area is the integration of geologic, geophysical, and geochemical field data into an effective suite of exploration tools that can support the delineation and characterization commercial gas hydrate prospects prior to drilling. The fourth primary research focus is the development and testing of well-based extraction technologies (including drilling, completion, stimulation and production) that can safely deliver commercial gas production rates from gas hydrate reservoirs in a variety of settings. Initial efforts will take advantage of the

  10. Gas hydrate single-crystal structure analyses.

    PubMed

    Kirchner, Michael T; Boese, Roland; Billups, W Edward; Norman, Lewis R

    2004-08-04

    The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.

  11. Ground movements associated with gas hydrate production

    SciTech Connect

    Siriwardane, H.J.

    1992-10-01

    The mechanics of ground movements during hydrate production can be more closely simulated by considering similarities with ground movements associated with subsidence in permafrost regions than with gob compaction in a longwall mine. The purpose of this research work is to investigate the potential strata movements associated with hydrate production by considering similarities with ground movements in permafrost regions. The work primarily involves numerical modeling of subsidence caused by hydrate dissociation. The investigation is based on the theories of continuum mechanics , thermomechanical behavior of frozen geo-materials, and principles of rock mechanics and geomechanics. It is expected that some phases of the investigation will involve the use of finite element method, which is a powerful computer-based method which has been widely used in many areas of science and engineering. Parametric studies will be performed to predict expected strata movements and surface subsidence for different reservoir conditions and properties of geological materials. The results from this investigation will be useful in predicting the magnitude of the subsidence problem associated with gas hydrate production. The analogy of subsidence in permafrost regions may provide lower bounds for subsidence expected in hydrate reservoirs. Furthermore, it is anticipated that the results will provide insight into planning of hydrate recovery operations.

  12. Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

    SciTech Connect

    McGrail, B. Peter; Schaef, Herbert T.; White, Mark D.; Zhu, Tao; Kulkarni, Abhijeet S.; Hunter, Robert B.; Patil, Shirish L.; Owen, Antionette T.; Martin, P F.

    2007-09-01

    Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO2 for enhanced recovery of an unconventional but potentially very important source of natural gas, gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally. The EGHR (Enhanced Gas Hydrate Recovery) concept takes advantage of the physical and thermodynamic properties of mixtures in the H2O-CO2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a LCO2-Lw microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Small scale column experiments show injection of the emulsion into a CH4 hydrate rich sand results in the release of CH4 gas and the formation of CO2 hydrate

  13. Elastic properties of gas hydrate-bearing sediments

    USGS Publications Warehouse

    Lee, M.W.; Collett, T.S.

    2001-01-01

    Downhole-measured compressional- and shear-wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate-bearing sediments is as a pore-filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field-observed velocities; however, the weighted equation more accurately describes the compressional- and shear-wave velocities of gas hydrate-bearing sediments. A decrease of Poisson's ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson's ratio with a decrease in the sediment porosity. Poisson's ratios greater than 0.33 for gas hydrate-bearing sediments imply the unconsolidated nature of gas hydrate-bearing sediments at this well site. The seismic characteristics of gas hydrate-bearing sediments at this site can be used to compare and evaluate other gas hydrate-bearing sediments in the Arctic.

  14. Videos of Experiments from ORNL Gas Hydrate Research

    DOE Data Explorer

    Gas hydrate research performed by the Environmental Sciences Division utilizes the ORNL Seafloor Process Simulator, the Parr Vessel, the Sapphire Cell, a fiber optic distributed sensing system, and Raman spectroscopy. The group studies carbon sequestration in the ocean, desalination, gas hydrates in the solar system, and nucleation and dissociation kinetics. The videos available at the gas hydrates website are very short clips from experiments.

  15. Nucleation and Growth of Gas Hydrate in Natural Seawater

    NASA Astrophysics Data System (ADS)

    Holman, S. A.; Osegovic, J. P.; Young, J. C.; Max, M. D.; Ames, A. L.

    2003-12-01

    Large-scale nucleation of gas hydrate takes place when hydrate-forming gas and seawater are brought together under suitable pressure-temperature conditions or where dissolved hydrate-forming gas in saturated or near-saturated seawater is chilled or brought to higher pressures. Profuse formation of hydrate shells on gas bubbles and nucleation of at least five different forms of gas hydrate have been achieved in fresh natural seawater. Growth of masses of solid gas hydrate takes place when hydrate-forming gas reactant dissolved in seawater is brought into the vicinity of the hydrate. The gas concentration of the enriched water in the vicinity of hydrate is higher than the hydrate equilibrium gas concentration. Hydrate growth under these conditions is accelerated due to the chemical potential difference between the enriched water and the hydrate crystals, which induces mass flux of dissolved hydrate forming gas into new hydrate crystals. As long as water enriched in the hydrate-forming gas is circulated into the vicinity of the hydrate, growth proceeds into the water space. Experimental approaches for growth of examples of solid masses of hydrate are presented. Results of these experiments provide an insight into the growth of gas hydrate under natural conditions where interstitial water in marine sediments is captured by burial from open seawater, and where solid gas hydrate forms on the seafloor. By using fresh natural seawater, which is a chemically and materially complex fluid, our experiments in pressurized, refrigerated reactors should closely track the growth history of solid hydrate in the natural environment. In our model for hydrate growth in sediments, nearly complete pore fill by diagenetic hydrate can best be accomplished by nucleation of hydrate at a point source within the pore water or at a particular point on sediment particulate, with growth outward into the water space that is refreshed with ground water having high concentrations of hydrate

  16. Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation

    USGS Publications Warehouse

    Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.

    2013-01-01

    As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

  17. Shallow gas hydrate within the areas of subaquatic seepage

    SciTech Connect

    Ginsburg, G.; Soloviev, V. )

    1993-09-01

    Sedimentary framework of worldwide hydrate-bearing areas and structures of sediments containing hydrates suggest that fluid filtration is the major process responsible for its generation. A study of seepage-associated hydrate accumulations that are accessible without drilling is useful for gaining an understanding of subaquatic gas hydrate formation general. Localities of shallow hydrate are indicative of oil and gas content. They also may be hazardous for oil and gas field development. The paper presents the results of exploration of gas hydrate accumulations that associate with diapirs, mud volcanoes, faults, subaquatic canyons, and pockmarks in the Caspian, Black, Okhotsk, and Barents seas. Data acquisition included echo sounding, seismic survey, ground sampling geothermic measurements, chemical and isotopic analyses of gas and water, definition of water content, and measurement of equilibrium pressures and temperatures. Hydrate content in sediments of discovered accumulations was up to 30-40% by volume. Somewhere, hydrate rests immediately on the bottom. Hydrate accumulation requires not only gas but also water input. It may be filtering either water bringing dissolved gas or pore/sea water migrating to meet gas diffusing bottomward. The models of gas hydrate formation have been developed for both gas-saturated water and free gas. Isotopic composition of water oxygen mainly results from exchange with carbonate inclusions rather than from the effect of hydrate fractionation. It is possible to evaluate hydrate content in sediments from the amount and composition of water.

  18. Highly Compressed Free Gas in Deep-Water Natural Gas Hydrate Systems

    NASA Astrophysics Data System (ADS)

    Barth, G. A.

    2006-12-01

    Natural gas, predominantly methane, is stored in a highly compact form within solid gas hydrate. The large volume of free gas that can be liberated by dissociation of hydrate (at standard surface conditions) is a prominent aspect of this potential energy resource. In contrast, the highly compressed state of free gas under pressure-temperature conditions found in deep-water marine settings is rarely noted. To facilitate comparison of gas quantities present within and below the hydrate stability zone in marine gas hydrate systems, particularly those in the deep-water Bering Sea basins, a suite of volume expansion ratios for 100% methane gas have been calculated. These ratios relate free gas volume under in-situ pressure (P) and temperature (T) conditions to free gas volume at standard surface conditions. The volume calculation is routine, using the Peng-Robinson equation of state (Peng and Robinson, 1976). Because most geophysical field studies aim to resolve the quantities of solid hydrate or free gas as a volume fraction of bulk rock in-situ, whereas gas resource volumes are reported as volume of free gas at STP, results here are presented as free gas volume ratios describing expansion between depth and surface conditions. This presentation also allows direct comparison with free gas yield of solid hydrate. Volume expansion ratio is presented for general reference for the pressure range 1 to 60 MPa and temperature range 0° to 80°C. (See USGS Open File Report 05-1451 online.) For pressures in the range 30 to 52 MPa and temperatures from 4° to 80°C, a more detailed evaluation of the P (water depth) and T (geotherm) effects on gas volumes has been undertaken. Ideal gas deviation factors, or z-factors, are also included. For free methane gas near the base of the hydrate stability zone at 360 m below seafloor in the Bering Sea, under conditions of 3,600 m water depth, 4°C seafloor temperature and 60°C/km geothermal gradient, the ratio of gas volume at standard

  19. Gas hydrate prospecting using well cuttings and mud-gas geochemistry from 35 wells, North Slope, Alaska

    USGS Publications Warehouse

    Lorenson, T.D.; Collett, Timothy S.

    2011-01-01

    Gas hydrate deposits are common on the North Slope of Alaska around Prudhoe Bay; however, the extent of these deposits is unknown outside of this area. As part of a U.S. Geological Survey (USGS) and Bureau of Land Management gas hydrate research collaboration, well-cutting and mud-gas samples have been collected and analyzed from mainly industry-drilled wells on the North Slope for the purpose of prospecting for gas hydrate deposits. On the Alaska North Slope, gas hydrates are now recognized as an element within a petroleum systems approach or "total petroleum system." Since 1979, 35 wells have been sampled from as far west as Wainwright to Prudhoe Bay in the east. Regionally, the USGS has assessed the gas hydrate resources of the North Slope and determined that there is about 85.4 trillion cubic feet of technically recoverable hydrate-bound gas within three assessment units. The assessment units are defined mainly by three separate stratigraphic sections and constrained by the physical temperatures and pressures where gas hydrate can form. Geochemical studies of known gas hydrate occurrences on the North Slope have shown a link between gas hydrate and more deeply buried conventional oil and gas deposits. The link is established when hydrocarbon gases migrate from depth and charge the reservoir rock within the gas hydrate stability zone. It is likely gases migrated into conventional traps as free gas and were later converted to gas hydrate in response to climate cooling concurrent with permafrost formation. Results from this study indicate that some thermogenic gas is present in 31 of the wells, with limited evidence of thermogenic gas in four other wells and only one well with no thermogenic gas. Gas hydrate is known to occur in one of the sampled wells, likely present in 22 others on the basis of gas geochemistry, and inferred by equivocal gas geochemistry in 11 wells, and one well was without gas hydrate. Gas migration routes are common in the North Slope and

  20. Hydrate Formation in Gas-Rich Marine Sediments: A Grain-Scale Model

    NASA Astrophysics Data System (ADS)

    Holtzman, R.; Juanes, R.

    2009-12-01

    We present a grain-scale model of marine sediment, which couples solid- and multiphase fluid-mechanics together with hydrate kinetics. The model is applied to investigate the spatial distribution of the different methane phases - gas and hydrate - within the hydrate stability zone. Sediment samples are generated from three-dimensional packs of spherical grains, mapping the void space into a pore network by tessellation. Gas invasion into the water-saturated sample is simulated by invasion-percolation, coupled with a discrete element method that resolves the grain mechanics. The coupled model accounts for forces exerted by the fluids, including cohesion associated with gas-brine surface tension. Hydrate growth is represented by a hydrate film along the gas-brine interface, which increases sediment cohesion by cementing the grain contacts. Our model of hydrate growth includes the possible rupture of the hydrate layer, which leads to the creation of new gas-water interface. In previous work, we have shown that fine-grained sediments (FGS) exhibit greater tendency to fracture, whereas capillary invasion is the preferred mode of methane gas transport in coarse-grained sediments (CGS). The gas invasion pattern has profound consequences on the hydrate distribution: a larger area-to-volume ratio of the gas cluster leads to a larger drop in gas pressure inside the growing hydrate shell, causing it to rupture. Repeated cycles of imbibition and hydrate growth accompanied by trapping of gas allow us to determine the distribution of hydrate and gas within the sediment as a function of time. Our pore-scale model suggests that, even when film rupture takes place, the conversion of gas to hydrate is slow. This explains two common field observations: the coexistence of gas and hydrate within the hydrate stability zone in CGS, and the high methane fluxes through fracture conduits in FGS. These results demonstrate the importance of accounting for the strong coupling among multiphase

  1. Distribution and controls on gas hydrate in the ocean-floor environment

    SciTech Connect

    Dillon, W.P.

    1995-12-31

    Methane hydrate, a crystalline solid that is formed of water and gas molecules, is widespread in oceanic sediments. It occurs at water depths that exceed 300 to 500 m and in a zone that commonly extends from the sea floor, down several hundred meters - the base of the zone is limited by increased temperature. To determine factors that control gas hydrate concentration, we have mapped its distribution off the U.S. Atlantic coast using acoustic remote-sensing methods. Most natural gas hydrate is formed from biogenic methane, and therefore it is concentrated where there is a rapid accumulation of organic detritus and also where there is a rapid accumulation of sediments (which protect detritus from oxidation). When hydrate fills the pore space of sediment, it can reduce permeability and create a gas trap. Such trapping of gas beneath hydrate may cause the formation of the most concentrated hydrate deposits, perhaps because the gas that is held in the trap can slowly diffuse upwards or migrate through faults. Hydrate-sealed traps are formed by hills on the sea floor, by dipping strata, or by salt(?) domes. Off the southeastern United States, a small area (only 3000 km{sup 2}) beneath a ridge formed by rapidly-deposited sediments appears to contain a volume of methane in hydrate that is equivalent to {approximately}30 times the U.S. annual consumption of gas. The breakdown of hydrate can cause submarine landslides by converting the hydrate to gas plus water and generating a rise of pore pressure. Conversely, sea-floor landslides can cause breakdown of hydrate by reducing the pressure in sediments. These interacting processes may cause cascading slides, which would result in breakdown of hydrate and release of methane to the atmosphere. This addition of methane to the global greenhouse would significantly influence climate. Gas hydrate in sea-floor sediments is potentially significant to climate, energy resources, and sea-floor stability.

  2. Oil & Natural Gas Technology A new approach to understanding the occurrence and volume of natural gas hydrate in the northern Gulf of Mexico using petroleum industry well logs

    SciTech Connect

    Cook, Ann; Majumdar, Urmi

    2016-03-31

    The northern Gulf of Mexico has been the target for the petroleum industry for exploration of conventional energy resource for decades. We have used the rich existing petroleum industry well logs to find the occurrences of natural gas hydrate in the northern Gulf of Mexico. We have identified 798 wells with well log data within the gas hydrate stability zone. Out of those 798 wells, we have found evidence of gas hydrate in well logs in 124 wells (15% of wells). We have built a dataset of gas hydrate providing information such as location, interval of hydrate occurrence (if any) and the overall quality of probable gas hydrate. Our dataset provides a wide, new perspective on the overall distribution of gas hydrate in the northern Gulf of Mexico and will be the key to future gas hydrate research and prospecting in the area.

  3. Study on propane-butane gas storage by hydrate technology

    NASA Astrophysics Data System (ADS)

    Hamidi, Nurkholis; Wijayanti, Widya; Widhiyanuriyawan, Denny

    2016-03-01

    Different technology has been applied to store and transport gas fuel. In this work the storage of gas mixture of propane-butane by hydrate technology was studied. The investigation was done on the effect of crystallizer rotation speed on the formation of propane-butane hydrate. The hydrates were formed using crystallizer with rotation speed of 100, 200, and 300 rpm. The formation of gas hydrates was done at initial pressure of 3 bar and temperature of 274K. The results indicated that the higher rotation speed was found to increase the formation rate of propane-butane hydrate and improve the hydrates stability.

  4. Strategies for gas hydrate exploration in the gulf of mexico

    NASA Astrophysics Data System (ADS)

    Johnson, A.; Dillon, W.; Max, M.

    2003-04-01

    Drilling results from Japan and the Canadian Arctic have demonstrated the potential for commercial production of natural gas from gas hydrate. Commercial gas hydrate methane production is likely within less than 10 years on a limited basis. A number of factors make the Gulf of Mexico (GOM) a significant area of interest for gas hydrate exploration. First, gas hydrate reaches its maximum concentrations in coarse clastics, and deposition in the GOM has provided for substantial amounts of sandy beds within the zone of hydrate stability. Second, the GOM has a high gas flux rate and an extensive system of migration paths, resulting in a high probability of multiple reservoirs with gas hydrate in the hydrate stability zone and gas deposits immediately below. Third, the existing infrastructure of platforms and pipelines improves the economics of hydrate development through the leveraging of existing facilities. Fourth, the GOM lies in a region of favorable political climate for exploitation of hydrocarbon deposits. Fifth, technology required for exploitation of gas hydrate is now emerging. Exploring for gas hydrates in the GOM requires the establishment of models for hydrate development and natural gas extraction. Ideally, such models integrate seismic, well log, and core data from throughout the subsurface hydrate stability zone. Unfortunately, few wells have been adequately logged in the hydrate stability zone interval in the Gulf and models are incomplete. Moreover, standard processing approaches for seismic data do not allow satisfactory assessment of hydrate occurrences. As a result, published models are presently derived mainly from piston core data and observations from submersibles. This near-seafloor information may be strongly misleading with respect to more deeply buried hydrate concentrations. The integration of a more stratigraphic approach to the Gulf's subsurface models and recognition of the importance of the hydrate cap could yield substantial new

  5. Experimental Study of Gas Hydrate Dynamics

    NASA Astrophysics Data System (ADS)

    Fandino, O.; Ruffine, L.

    2011-12-01

    Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine

  6. Geophysics Characteristic on Gas Hydrates Zone in Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Sha, Zhibin

    2015-04-01

    Gas hydrates are very important because of their vast resources potential, their roles as submarine geohazard, and their effects on global climate in the word. In China, the research of gas hydrates was initiated further later ,but the South China Sea has found a number of geophysical anomalies of gas hydrate by researching of almost 10 years. In order to determine the nature and distribution of marine gas hydrate, a series of geophysical techniques are used. By using the traditional seismic data processing, purpose seismic data processing, wave impedance inversion techniques and geophysical well logging data processing based on Self-organizing feature map neural network, a great deal of useful information are abstracted to determine the gas hydrate zone beneath the seabed. The results show (1) Conventional multi-channel seismic reflection processing data from the SCS reveal various seismic indicators of gas hydrate and associated gas, such as the BSR, enhanced reflections below the BSR, Weak reflection or blanking zone above the BSRs.;(2) special processing techniques, such as attribute extraction and wave impedance inversion, is necessary so as to mine more effective data, they could compensate the shortage of conventional seismic data processing techniques used for distinguishing gas-bearing reservoirs;(3) as a kind of intelligent information processing technology, SOFM neural network is feasible for lithologic identification by logging data and has a high rate of identification of gas hydrate. In the end, the author hopes it may provide some useful clues to the exploration of gas hydrate.

  7. Assessing Gas-Hydrate Prospects on the North Slope of Alaska - Theoretical Considerations

    USGS Publications Warehouse

    Lee, Myung W.; Collett, Timothy S.; Agena, Warren F.

    2008-01-01

    Gas-hydrate resource assessment on the Alaska North Slope using 3-D and 2-D seismic data involved six important steps: (1) determining the top and base of the gas-hydrate stability zone, (2) 'tying' well log information to seismic data through synthetic seismograms, (3) differentiating ice from gas hydrate in the permafrost interval, (4) developing an acoustic model for the reservoir and seal, (5) developing a method to estimate gas-hydrate saturation and thickness from seismic attributes, and (6) assessing the potential gas-hydrate prospects from seismic data based on potential migration pathways, source, reservoir quality, and other relevant geological information. This report describes the first five steps in detail using well logs and provides theoretical backgrounds for resource assessments carried out by the U.S. Geological Survey. Measured and predicted P-wave velocities enabled us to tie synthetic seismograms to the seismic data. The calculated gas-hydrate stability zone from subsurface wellbore temperature data enabled us to focus our effort on the most promising depth intervals in the seismic data. A typical reservoir in this area is characterized by the P-wave velocity of 1.88 km/s, porosity of 42 percent, and clay volume content of 5 percent, whereas seal sediments encasing the reservoir are characterized by the P-wave velocity of 2.2 km/s, porosity of 32 percent, and clay volume content of 20 percent. Because the impedance of a reservoir without gas hydrate is less than that of the seal, a complex amplitude variation with respect to gas-hydrate saturation is predicted, namely polarity change, amplitude blanking, and high seismic amplitude (a bright spot). This amplitude variation with gas-hydrate saturation is the physical basis for the method used to quantify the resource potential of gas hydrates in this assessment.

  8. Evaluation of long-term gas hydrate production testing locations on the Alaska north slope

    USGS Publications Warehouse

    Collett, T.S.; Boswell, R.; Lee, M.W.; Anderson, B.J.; Rose, K.; Lewis, K.A.

    2011-01-01

    The results of short duration formation tests in northern Alaska and Canada have further documented the energy resource potential of gas hydrates and justified the need for long-term gas hydrate production testing. Additional data acquisition and long-term production testing could improve the understanding of the response of naturally-occurring gas hydrate to depressurization-induced or thermal-, chemical-, and/or mechanical-stimulated dissociation of gas hydrate into producible gas. The Eileen gas hydrate accumulation located in the Greater Prudhoe Bay area in northern Alaska has become a focal point for gas hydrate geologic and production studies. BP Exploration (Alaska) Incorporated and ConocoPhillips have each established research partnerships with U.S. Department of Energy to assess the production potential of gas hydrates in northern Alaska. A critical goal of these efforts is to identify the most suitable site for production testing. A total of seven potential locations in the Prudhoe Bay, Kuparuk, and Milne Point production units were identified and assessed relative to their suitability as a long-term gas hydrate production test site. The test site assessment criteria included the analysis of the geologic risk associated with encountering reservoirs for gas hydrate testing. The site selection process also dealt with the assessment of the operational/logistical risk associated with each of the potential test sites. From this review, a site in the Prudhoe Bay production unit was determined to be the best location for extended gas hydrate production testing. The work presented in this report identifies the key features of the potential test site in the Greater Prudhoe Bay area, and provides new information on the nature of gas hydrate occurrence and potential impact of production testing on existing infrastructure at the most favorable sites. These data were obtained from well log analysis, geological correlation and mapping, and numerical simulation

  9. Evaluation of long-term gas hydrate production testing locations on the Alaska North Slope

    USGS Publications Warehouse

    Collett, Timothy; Boswell, Ray; Lee, Myung W.; Anderson, Brian J.; Rose, Kelly K.; Lewis, Kristen A.

    2011-01-01

    The results of short duration formation tests in northern Alaska and Canada have further documented the energy resource potential of gas hydrates and justified the need for long-term gas hydrate production testing. Additional data acquisition and long-term production testing could improve the understanding of the response of naturally-occurring gas hydrate to depressurization-induced or thermal-, chemical-, and/or mechanical-stimulated dissociation of gas hydrate into producible gas. The Eileen gas hydrate accumulation located in the Greater Prudhoe Bay area in northern Alaska has become a focal point for gas hydrate geologic and production studies. BP Exploration (Alaska) Incorporated and ConocoPhillips have each established research partnerships with U.S. Department of Energy to assess the production potential of gas hydrates in northern Alaska. A critical goal of these efforts is to identify the most suitable site for production testing. A total of seven potential locations in the Prudhoe Bay, Kuparuk, and Milne Point production units were identified and assessed relative to their suitability as a long-term gas hydrate production test site. The test site assessment criteria included the analysis of the geologic risk associated with encountering reservoirs for gas hydrate testing. The site selection process also dealt with the assessment of the operational/logistical risk associated with each of the potential test sites. From this review, a site in the Prudhoe Bay production unit was determined to be the best location for extended gas hydrate production testing. The work presented in this report identifies the key features of the potential test site in the Greater Prudhoe Bay area, and provides new information on the nature of gas hydrate occurrence and potential impact of production testing on existing infrastructure at the most favorable sites. These data were obtained from well log analysis, geological correlation and mapping, and numerical simulation.

  10. Physical properties of sediment containing methane gas hydrate

    USGS Publications Warehouse

    Winters, W.J.; Waite, W.F.; Mason, D.H.; Gilbert, L.Y.

    2005-01-01

    A study conducted by the US Geological Survey (USGS) on the formation, behavior, and properties of mixtures of gas hydrate and sediment is presented. The results show that the properties of host material influence the type and quantity of hydrates formed. The presence of hydrate during mechanical shear tests affects the measured sediment pore pressure. Sediment shear strength may be increased more than 500 percent by intact hydrate, but greatly weakened if the hydrate dissociates.

  11. Resources assessment of methane hydrates offshore Japan

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.

    2015-12-01

    JOGMEC, as a member of research group for resources assessment of Research Consortium for Methane Hydrate Resources in Japan (MH21), is conducting resources assessment of methane hydrates (MHs) offshore surrounding Japan. The interpretation of 3-D seismic data acquired by geophysical vessel 'Shigen', which is owned by Agency for Natural Resources and Energy, are carried out. And MH concentrated zones are being extracted. This study is an introduction for the case example of interpretation of 3-D seismic data in the area which have not been drilled. The characteristic of 3-D seismic data in this study area shows fold structure, which undulates severalfold. In addition, some faults are interpreted, which does not show the large displacement, are seen. Bottom Simulating Reflector (BSR) is very visible continuously. Clear velocity contrast in the boundary between above and below of BSR and the high velocity anomaly above BSR are confirmed in the high density velocity analysis profile. MHs are assumed to exist in sand heterogeneously because the velocity distribution in the extracted zones is inhomogeneous. In the results of geomorphological analysis, channel deposits and mid submarine fan deposits, which are located above BSR, are presumed the sediments which bear sand. Thus the extracted zones are estimated MH concentrated zones. As above, even the area has not been drilled, the extraction of MH concentrated zones can be estimated by the interpretation of the seismic data, the result of the high density velocity analysis, and the distribution of sand by geomorphological analysis. These results will be useful for the plan of the future drilling programme. This introduction is the example of 3-D seismic survey area. It will become a useful information for 3-D seismic survey plan by performing similar interpretation in 2-D seismic survey lines.

  12. Arctic Gas hydrate, Environment and Climate

    NASA Astrophysics Data System (ADS)

    Mienert, Jurgen; Andreassen, Karin; Bünz, Stefan; Carroll, JoLynn; Ferre, Benedicte; Knies, Jochen; Panieri, Giuliana; Rasmussen, Tine; Myhre, Cathrine Lund

    2015-04-01

    Arctic methane hydrate exists on land beneath permafrost regions and offshore in shelf and continental margins sediments. Methane or gas hydrate, an ice-like substrate, consists mainly of light hydrocarbons (mostly methane from biogenic sources but also ethane and propane from thermogenic sources) entrapped by a rigid cage of water molecules. The pressure created by the overlying water and sediments offshore stabilizes the CH4 in continental margins at a temperature range well above freezing point; consequently CH4 exists as methane ice beneath the seabed. Though the accurate volume of Arctic methane hydrate and thus the methane stored in hydrates throughout the Quaternary is still unknown it must be enormous if one considers the vast regions of Arctic continental shelves and margins as well as permafrost areas offshore and on land. Today's subseabed methane hydrate reservoirs are the remnants from the last ice age and remain elusive targets for both unconventional energy and as a natural methane emitter influencing ocean environments and ecosystems. It is still contentious at what rate Arctic warming may govern hydrate melting, and whether the methane ascending from the ocean floor through the hydrosphere reaches the atmosphere. As indicated by Greenland ice core records, the atmospheric methane concentration rose rapidly from ca. 500 ppb to ca. 750 ppb over a short time period of just 150 years at the termination of the younger Dryas period ca. 11600 years ago, but the dissociation of large quantities of methane hydrates on the ocean floor have not been documented yet (Brook et al., 2014 and references within). But with the major projected warming and sea ice melting trend (Knies et al., 2014) one may ask, for how long will CH4 stay trapped in methane hydrates if surface and deep-ocean water masses will warm and permafrost continuous to melt (Portnov et al. 2014). How much of the Arctic methane will be consumed by the micro- and macrofauna, how much will

  13. Petrophysical Characterization and Reservoir Simulator for Methane Gas Production from Gulf of Mexico Hydrates

    SciTech Connect

    Kishore Mohanty; Bill Cook; Mustafa Hakimuddin; Ramanan Pitchumani; Damiola Ogunlana; Jon Burger; John Shillinglaw

    2006-06-30

    Gas hydrates are crystalline, ice-like compounds of gas and water molecules that are formed under certain thermodynamic conditions. Hydrate deposits occur naturally within ocean sediments just below the sea floor at temperatures and pressures existing below about 500 meters water depth. Gas hydrate is also stable in conjunction with the permafrost in the Arctic. Most marine gas hydrate is formed of microbially generated gas. It binds huge amounts of methane into the sediments. Estimates of the amounts of methane sequestered in gas hydrates worldwide are speculative and range from about 100,000 to 270,000,000 trillion cubic feet (modified from Kvenvolden, 1993). Gas hydrate is one of the fossil fuel resources that is yet untapped, but may play a major role in meeting the energy challenge of this century. In this project novel techniques were developed to form and dissociate methane hydrates in porous media, to measure acoustic properties and CT properties during hydrate dissociation in the presence of a porous medium. Hydrate depressurization experiments in cores were simulated with the use of TOUGHFx/HYDRATE simulator. Input/output software was developed to simulate variable pressure boundary condition and improve the ease of use of the simulator. A series of simulations needed to be run to mimic the variable pressure condition at the production well. The experiments can be matched qualitatively by the hydrate simulator. The temperature of the core falls during hydrate dissociation; the temperature drop is higher if the fluid withdrawal rate is higher. The pressure and temperature gradients are small within the core. The sodium iodide concentration affects the dissociation pressure and rate. This procedure and data will be useful in designing future hydrate studies.

  14. Critical pressure and multiphase flow in Blake Ridge gas hydrates

    USGS Publications Warehouse

    Flemings, P.B.; Liu, Xiuying; Winters, W.J.

    2003-01-01

    We use core porosity, consolidation experiments, pressure core sampler data, and capillary pressure measurements to predict water pressures that are 70% of the lithostatic stress, and gas pressures that equal the lithostatic stress beneath the methane hydrate layer at Ocean Drilling Program Site 997, Blake Ridge, offshore North Carolina. A 29-m-thick interconnected free-gas column is trapped beneath the low-permeability hydrate layer. We propose that lithostatic gas pressure is dilating fractures and gas is migrating through the methane hydrate layer. Overpressured gas and water within methane hydrate reservoirs limit the amount of free gas trapped and may rapidly export methane to the seafloor.

  15. The Role of Bottom Simulating Reflectors in Gas Hydrate Assessment

    NASA Astrophysics Data System (ADS)

    Majumdar, U.; Shedd, W. W.; Cook, A.; Frye, M.

    2015-12-01

    In this research we test the viability of using a bottom simulating reflector (BSR) to detect gas hydrate. Bottom simulating reflectors (BSRs) occur at many gas hydrate sites near the thermodynamic base of the gas hydrate stability zone (GHSZ), and are frequently used to identify possible presence of gas hydrate on a regional scale. To find if drilling a BSR actually increases the chances of finding gas hydrate, we combine an updated dataset of BSR distribution from the Bureau of Ocean Energy Management with a comprehensive dataset of natural gas hydrate distribution as appraised from well logs, covering an area of around 200,000 square kilometers in the northern Gulf of Mexico. The BSR dataset compiles industry 3-D seismic data, and includes mostly good-quality and high-confidence traditional and non-traditional BSRs. Resistivity well logs were used to identify the presence of gas hydrate from over 700 existing industry wells and we have found over 110 wells with likely gas hydrate occurrences. By integrating the two datasets, our results show that the chances of encountering gas hydrate when drilling through a BSR is ~ 42%, while that when drilling outside the BSR is ~15%. Our preliminary analysis indicates that a positive relationship exists between BSRs and gas hydrate accumulations, and the chances of encountering gas hydrate increases almost three-fold when drilling through a BSR. One interesting observation is that ~ 58% of the wells intersecting a BSR show no apparent evidence of gas hydrate. In this case, a BSR may occur at sites with no gas hydrate accumulations due to the presence of very low concentration of free gas that is not detected on resistivity logs. On the other hand, in a few wells, accumulations of gas hydrate were observed where no BSR is present. For example in a well in Atwater Valley Block 92, two intervals of gas hydrate accumulation in fractures have been identified on resistivity logs, of which, the deeper interval has 230 feet thick

  16. Development of hydrate risk quantification in oil and gas production

    NASA Astrophysics Data System (ADS)

    Chaudhari, Piyush N.

    Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in

  17. Natural gas hydrates on the North Slope of Alaska

    SciTech Connect

    Collett, T.S.

    1991-01-01

    Gas hydrates are crystalline substances composed of water and gas, mainly methane, in which a solid-water lattice accommodates gas molecules in a cage-like structure, or clathrate. These substances often have been regarded as a potential (unconventional) source of natural gas. Significant quantities of naturally occurring gas hydrates have been detected in many regions of the Arctic including Siberia, the Mackenzie River Delta, and the North Slope of Alaska. On the North Slope, the methane-hydrate stability zone is areally extensive beneath most of the coastal plain province and has thicknesses as great as 1000 meters in the Prudhoe Bay area. Gas hydrates have been identified in 50 exploratory and production wells using well-log responses calibrated to the response of an interval in one well where gas hydrates were recovered in a core by ARCO Alaska and EXXON. Most of these gas hydrates occur in six laterally continuous Upper Cretaceous and lower Tertiary sandstone and conglomerate units; all these gas hydrates are geographically restricted to the area overlying the eastern part of the Kuparuk River Oil Field and the western part of the Prudhoe Bay Oil Field. The volume of gas within these gas hydrates is estimated to be about 1.0 {times} 10{sup 12} to 1.2 {times} 10{sup 12} cubic meters (37 to 44 trillion cubic feet), or about twice the volume of conventional gas in the Prudhoe Bay Field. Geochemical analyses of well samples suggest that the identified hydrates probably contain a mixture of deep-source thermogenic gas and shallow microbial gas that was either directly converted to gas hydrate or first concentrated in existing traps and later converted to gas hydrate. The thermogenic gas probably migrated from deeper reservoirs along the same faults thought to be migration pathways for the large volumes of shallow, heavy oil that occur in this area. 51 refs., 11 figs., 3 tabs.

  18. Natural Gas Evolution in a Gas Hydrate Melt: Effect of Thermodynamic Hydrate Inhibitors.

    PubMed

    Sujith, K S; Ramachandran, C N

    2017-01-12

    Natural gas extraction from gas hydrate sediments by injection of hydrate inhibitors involves the decomposition of hydrates. The evolution of dissolved gas from the hydrate melt is an important step in the extraction process. Using classical molecular dynamics simulations, we study the evolution of dissolved methane from its hydrate melt in the presence of two thermodynamic hydrate inhibitors, NaCl and CH3OH. An increase in the concentration of hydrate inhibitors is found to promote the nucleation of methane nanobubbles in the hydrate melt. Whereas NaCl promotes bubble formation by enhancing the hydrophobic interaction between aqueous CH4 molecules, CH3OH molecules assist bubble formation by stabilizing CH4 bubble nuclei formed in the solution. The CH3OH molecules accumulate around the nuclei leading to a decrease in the surface tension at their interface with water. The nanobubbles formed are found to be highly dynamic with frequent exchange of CH4 molecules between the bubble and the surrounding liquid. A quantitative analysis of the dynamic behavior of the bubble is performed by introducing a unit step function whose value depends on the location of CH4 molecules with respect to the bubble. It is observed that an increase in the concentration of thermodynamic hydrate inhibitors reduces the exchange process, making the bubble less dynamic. It is also found that for a given concentration of the inhibitor, larger bubbles are less dynamic compared to smaller ones. The dependence of the dynamic nature of nanobubbles on bubble size and inhibitor concentration is correlated with the solubility of CH4 and the Laplace pressure within the bubble. The effect of CO2 on the formation of nanobubble in the CH4-CO2 mixed gas hydrate melt in the presence of inhibitors is also examined. The simulations show that the presence of CO2 molecules significantly reduces the induction time for methane nanobubble nucleation. The role of CO2 in the early nucleation of bubble is explained

  19. Effective-Medium Models for Marine Gas Hydrates, Mallik Revisited

    NASA Astrophysics Data System (ADS)

    Terry, D. A.; Knapp, C. C.; Knapp, J. H.

    2011-12-01

    Hertz-Mindlin type effective-medium dry-rock elastic models have been commonly used for more than three decades in rock physics analysis, and recently have been applied to assessment of marine gas hydrate resources. Comparisons of several effective-medium models with derivative well-log data from the Mackenzie River Valley, Northwest Territories, Canada (i.e. Mallik 2L-38 and 5L-38) were made several years ago as part of a marine gas hydrate joint industry project in the Gulf of Mexico. The matrix/grain supporting model (one of the five models compared) was clearly a better representation of the Mallik data than the other four models (2 cemented sand models; a pore-filling model; and an inclusion model). Even though the matrix/grain supporting model was clearly better, reservations were noted that the compressional velocity of the model was higher than the compressional velocity measured via the sonic logs, and that the shear velocities showed an even greater discrepancy. Over more than thirty years, variations of Hertz-Mindlin type effective medium models have evolved for unconsolidated sediments and here, we briefly review their development. In the past few years, the perfectly smooth grain version of the Hertz-Mindlin type effective-medium model has been favored over the infinitely rough grain version compared in the Gulf of Mexico study. We revisit the data from the Mallik wells to review assertions that effective-medium models with perfectly smooth grains are a better predictor than models with infinitely rough grains. We briefly review three Hertz-Mindlin type effective-medium models, and standardize nomenclature and notation. To calibrate the extended effective-medium model in gas hydrates, we use a well accepted framework for unconsolidated sediments through Hashin-Shtrikman bounds. We implement the previously discussed effective-medium models for saturated sediments with gas hydrates and compute theoretical curves of seismic velocities versus gas hydrate

  20. Catastrophic growth of gas hydrates in the presence of kinetic hydrate inhibitors.

    PubMed

    Cha, Minjun; Shin, Kyuchul; Seo, Yutaek; Shin, Ju-Young; Kang, Seong-Pil

    2013-12-27

    The effect of the concentration of kinetic hydrate inhibitors, polyvinylpyrrolidone (PVP), and polyvinylcaprolactam (PVCap) on the onset and growth of synthetic natural gas hydrates is investigated by measuring the hydrate onset time and gas consumption rate. Although the hydrate onset time is extended by increasing the concentration from 0.5 to 3.0 wt % for both PVP and PVCap, the growth rate of hydrates shows that the different tendency depends on the type of kinetic hydrate inhibitor and its concentration. For PVCap solution, the hydrate growth was slow for more than 1000 min after the onset at the concentration of 0.5 and 1.5 wt %. However, the growth rate becames almost 8 times faster at the concentration of 3.0 wt %, representing the catastrophic growth of hydrate just after the hydrate onset. (13)C NMR spectra of hydrates formed at 3.0 wt % of PVP and PVCap indicate the existence of both structures I and II. Cage occupancy of methane in large cages of structure II decreases significantly when compared to that for pure water. These results suggest that increasing the concentration of KHI up to 3.0 wt % may induce the earlier appearance of catastrophic hydrate growth and the existence of metastable structure I; thus, there needs to be an upper limit for using KHI to manage the formation of gas hydrates.

  1. Evaluation of long-term gas hydrate production testing locations on the Alaska North Slope

    USGS Publications Warehouse

    Collett, Timothy S.; Boswell, Ray; Lee, Myung W.; Anderson, Brian J.; Rose, Kelly K.; Lewis, Kristen A.

    2012-01-01

    The results of short-duration formation tests in northern Alaska and Canada have further documented the energy-resource potential of gas hydrates and have justified the need for long-term gas-hydrate-production testing. Additional data acquisition and long-term production testing could improve the understanding of the response of naturally occurring gas hydrate to depressurization-induced or thermal-, chemical-, or mechanical-stimulated dissociation of gas hydrate into producible gas. The Eileen gashydrate accumulation located in the Greater Prudhoe Bay area in northern Alaska has become a focal point for gas-hydrate geologic and production studies. BP Exploration (Alaska) Incorporated and ConocoPhillips have each established research partnerships with the US Department of Energy to assess the production potential of gas hydrates in northern Alaska. A critical goal of these efforts is to identify the most suitable site for production testing. A total of seven potential locations in the Prudhoe Bay, Kuparuk River, and Milne Point production units were identified and assessed relative to their suitability as a long-term gas-hydrate-production test sites. The test-site-assessment criteria included the analysis of the geologic risk associated with encountering reservoirs for gas-hydrate testing. The site-selection process also dealt with the assessment of the operational/logistical risk associated with each of the potential test sites. From this review, a site in the Prudhoe Bay production unit was determined to be the best location for extended gas-hydrate-production testing. The work presented in this report identifies the key features of the potential test site in the Greater Prudhoe Bay area and provides new information on the nature of gas-hydrate occurrence and the potential impact of production testing on existing infrastructure at the most favorable sites. These data were obtained from well-log analysis, geological correlation and mapping, and numerical

  2. Gas phase hydration of organic ions.

    PubMed

    Momoh, Paul O; El-Shall, M Samy

    2008-08-28

    In this work, we study the hydration phenomenon on a molecular level in the gas phase where a selected number of water molecules can interact with the organic ion of interest. The stepwise binding energies (DeltaH degrees (n-1,n)) of 1-7 water molecules to the phenyl acetylene cation are determined by equilibrium measurements using an ion mobility drift cell. The stepwise hydration energies DeltaH degrees (n-1,n) are nearly constant at 39.7 +/- 6.3 kJ mol(-1) from n = 1 to 7. The entropy change is larger in the n = 7 step, suggesting cyclic or cage-like water structures. No water addition is observed on the ionized phenyl acetylene trimer consistent with cyclization of the trimer ion to form triphenyl benzene cations C(24)H(18) (+) which are expected to interact weakly with the water molecules due to steric interactions and the delocalization of the charge on the large organic ion. The work demonstrates that hydration studies of organic ions can provide structural information on the organic ions.

  3. Compound Natural Gas Hydrate: A Natural System for Separation of Hydrate-Forming Gases

    NASA Astrophysics Data System (ADS)

    Max, M. D.; Osegovic, J. P.

    2007-12-01

    Natural processes that separate materials from a mixture may exert a major influence on the development of the atmospheres and surfaces of planets, moons, and other planetary bodies. Natural distillation and gravity separation, amongst others, are well known means of differentiating materials through liquid-gas partitioning. One of the least known attributes of clathrate (gas) hydrates is their potential effect on the evolution of planetary system oceans and atmospheres. Gas hydrates separate gases from mixtures of gases by concentrating preferred hydrate-forming materials (HFM) guests within the water-molecule cage structure of crystalline hydrate. Different HFMs have very different fields of stability. When multiple hydrate formers are present, a preference series based on their selective uptake exists. Compound hydrate, which is formed from two or more species of HFM, extract preferred HFM from a mixture in very different proportions to their relative percentages of the original mixture. These compound hydrates can have different formation and dissociation conditions depending on the evolution of the environment. That is, the phase boundary of the compound hydrate that is required for dissociation lies along a lower pressure - higher temperature course. Compound hydrates respond to variations in temperature, pressure, and HFM composition. On Earth, the primary naturally occurring hydrate of interest to global climate modeling is methane hydrate. Oceanic hydrate on Earth is the largest store of carbon in the biosphere that is immediately reactive to environmental change, and is capable of releasing large amounts of methane into the atmosphere over a short geological time span. Hydrate formation is essentially metastable and is very sensitive to environmental change and to gas flux. Where natural variations in temperature and pressure varies so that hydrate will form and dissociate in some cyclical manner, such as in oceans where sea level is capable of rising and

  4. Controls on gas hydrate stability in methane depleted sediments: Laboratory and field measurements

    NASA Astrophysics Data System (ADS)

    Lapham, L.; Chanton, J.; Martens, C. S.

    2009-12-01

    Gas hydrate deposits are the Earth’s largest reservoir of the powerful greenhouse gas methane and thus a key future energy resource. However, hydrate stability in sedimentary environments featuring highly variable methane concentrations needs to be understood to allow resource estimation and recovery. Hydrates are at chemical equilibrium and therefore stable where high pressures, low temperatures, and moderate salinities coexist with methane-saturated pore waters. When all of these conditions are not met, hydrates should dissociate or dissolve, releasing methane to the overlying water and possibly the atmosphere. In addition, other natural factors may control the kinetics of their degradation complicating models for hydrate stability and occurrence. Our measurements indicate that the pore-waters surrounding some shallow buried hydrates are not methane-saturated suggesting that dissolution should occur relatively rapidly. Yet, these hydrate deposits are known to persist relatively unchanged for years. We hypothesize that, once formed, hydrate deposits may be stabilized by natural factors inhibiting dissolution, including oil or microbial biofilm coatings. While most studies have focused on pressure and temperature changes where hydrates occur, relatively few have included measurements of in situ methane concentration gradients because of the difficulties inherent to making such measurements. Here we present recent measurements of methane concentration and stable carbon isotope gradients immediately adjacent to undisturbed hydrate surfaces obtained through deployments of novel seafloor instruments. Our results suggest that the hydrates studied are relatively stable when exposed to overlying and pore-waters that are undersaturated with methane. Concurrent laboratory measurements of methane concentration gradients next to artificial hydrate surfaces were utilized to test our protective coating hypothesis. After a stable dissolution rate for hydrate samples was

  5. Putting the Deep Biosphere and Gas Hydrates on the Map

    ERIC Educational Resources Information Center

    Sikorski, Janelle J.; Briggs, Brandon R.

    2016-01-01

    Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage…

  6. The characteristics of gas hydrates occurring in natural environment

    NASA Astrophysics Data System (ADS)

    Lu, H.; Moudrakovski, I.; Udachin, K.; Enright, G.; Ratcliffe, C.; Ripmeester, J.

    2009-12-01

    In the past few years, extensive analyses have been carried out for characterizing the natural gas hydrate samples from Cascadia, offshore Vancouver Island; Mallik, Mackenzie Delta; Mount Elbert, Alaska North Slope; Nankai Trough, offshore Japan; Japan Sea and offshore India. With the results obtained, it is possible to give a general picture of the characteristics of gas hydrates occurring in natural environment. Gas hydrate can occur in sediments of various types, from sands to clay, although it is preferentially enriched in sediments of certain types, for example coarse sands and fine volcanic ash. Most of the gas hydrates in sediments are invisible, occurring in the pores of the sediments, while some hydrates are visible, appearing as massive, nodular, planar, vein-like forms and occurring around the seafloor, in the fractures related to fault systems, or any other large spaces available in sediments. Although methane is the main component of most of the natural gas hydrates, C2 to C7 hydrocarbons have been recognized in hydrates, sometimes even in significant amounts. Shallow marine gas hydrates have been found generally to contain minor amounts of hydrogen sulfide. Gas hydrate samples with complex gas compositions have been found to have heterogeneous distributions in composition, which might reflect changes in the composition of the available gas in the surrounding environment. Depending on the gas compositions, the structure type of a natural gas hydrate can be structure I, II or H. For structure I methane hydrate, the large cages are almost fully occupied by methane molecules, while the small cages are only partly occupied. Methane hydrates occurring in different environments have been identified with almost the same crystallographic parameters.

  7. Alaska North Slope regional gas hydrate production modeling forecasts

    USGS Publications Warehouse

    Wilson, S.J.; Hunter, R.B.; Collett, T.S.; Hancock, S.; Boswell, R.; Anderson, B.J.

    2011-01-01

    A series of gas hydrate development scenarios were created to assess the range of outcomes predicted for the possible development of the "Eileen" gas hydrate accumulation, North Slope, Alaska. Production forecasts for the "reference case" were built using the 2002 Mallik production tests, mechanistic simulation, and geologic studies conducted by the US Geological Survey. Three additional scenarios were considered: A "downside-scenario" which fails to identify viable production, an "upside-scenario" describes results that are better than expected. To capture the full range of possible outcomes and balance the downside case, an "extreme upside scenario" assumes each well is exceptionally productive.Starting with a representative type-well simulation forecasts, field development timing is applied and the sum of individual well forecasts creating the field-wide production forecast. This technique is commonly used to schedule large-scale resource plays where drilling schedules are complex and production forecasts must account for many changing parameters. The complementary forecasts of rig count, capital investment, and cash flow can be used in a pre-appraisal assessment of potential commercial viability.Since no significant gas sales are currently possible on the North Slope of Alaska, typical parameters were used to create downside, reference, and upside case forecasts that predict from 0 to 71??BM3 (2.5??tcf) of gas may be produced in 20 years and nearly 283??BM3 (10??tcf) ultimate recovery after 100 years.Outlining a range of possible outcomes enables decision makers to visualize the pace and milestones that will be required to evaluate gas hydrate resource development in the Eileen accumulation. Critical values of peak production rate, time to meaningful production volumes, and investments required to rule out a downside case are provided. Upside cases identify potential if both depressurization and thermal stimulation yield positive results. An "extreme upside

  8. Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

    NASA Astrophysics Data System (ADS)

    Burchwell, A.; Cook, A.

    2015-12-01

    Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

  9. Well log characterization of natural gas-hydrates

    USGS Publications Warehouse

    Collett, Timothy S.; Lee, Myung W.

    2012-01-01

    In the last 25 years there have been significant advancements in the use of well-logging tools to acquire detailed information on the occurrence of gas hydrates in nature: whereas wireline electrical resistivity and acoustic logs were formerly used to identify gas-hydrate occurrences in wells drilled in Arctic permafrost environments, more advanced wireline and logging-while-drilling (LWD) tools are now routinely used to examine the petrophysical nature of gas-hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. Resistivity- and acoustic-logging tools are the most widely used for estimating the gas-hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. Recent integrated sediment coring and well-log studies have confirmed that electrical-resistivity and acoustic-velocity data can yield accurate gas-hydrate saturations in sediment grain-supported (isotropic) systems such as sand reservoirs, but more advanced log-analysis models are required to characterize gas hydrate in fractured (anisotropic) reservoir systems. New well-logging tools designed to make directionally oriented acoustic and propagation-resistivity log measurements provide the data needed to analyze the acoustic and electrical anisotropic properties of both highly interbedded and fracture-dominated gas-hydrate reservoirs. Advancements in nuclear magnetic resonance (NMR) logging and wireline formation testing (WFT) also allow for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids(i.e., free water along with clay- and capillary-bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms

  10. Methane gas hydrate effect on sediment acoustic and strength properties

    USGS Publications Warehouse

    Winters, W.J.; Waite, W.F.; Mason, D.H.; Gilbert, L.Y.; Pecher, I.A.

    2007-01-01

    To improve our understanding of the interaction of methane gas hydrate with host sediment, we studied: (1) the effects of gas hydrate and ice on acoustic velocity in different sediment types, (2) effect of different hydrate formation mechanisms on measured acoustic properties (3) dependence of shear strength on pore space contents, and (4) pore pressure effects during undrained shear. A wide range in acoustic p-wave velocities (Vp) were measured in coarse-grained sediment for different pore space occupants. Vp ranged from less than 1 km/s for gas-charged sediment to 1.77–1.94 km/s for water-saturated sediment, 2.91–4.00 km/s for sediment with varying degrees of hydrate saturation, and 3.88–4.33 km/s for frozen sediment. Vp measured in fine-grained sediment containing gas hydrate was substantially lower (1.97 km/s). Acoustic models based on measured Vp indicate that hydrate which formed in high gas flux environments can cement coarse-grained sediment, whereas hydrate formed from methane dissolved in the pore fluid may not. The presence of gas hydrate and other solid pore-filling material, such as ice, increased the sediment shear strength. The magnitude of that increase is related to the amount of hydrate in the pore space and cementation characteristics between the hydrate and sediment grains. We have found, that for consolidation stresses associated with the upper several hundred meters of sub-bottom depth, pore pressures decreased during shear in coarse-grained sediment containing gas hydrate, whereas pore pressure in fine-grained sediment typically increased during shear. The presence of free gas in pore spaces damped pore pressure response during shear and reduced the strengthening effect of gas hydrate in sands.

  11. Challenges, uncertainties, and issues facing gas production from gas-hydrate deposits

    USGS Publications Warehouse

    Moridis, G.J.; Collett, T.S.; Pooladi-Darvish, M.; Hancock, S.; Santamarina, C.; Boswel, R.; Kneafsey, T.; Rutqvist, J.; Kowalsky, M.B.; Reagan, M.T.; Sloan, E.D.; Sum, A.K.; Koh, C.A.

    2011-01-01

    The current paper complements the Moridis et al. (2009) review of the status of the effort toward commercial gas production from hydrates. We aim to describe the concept of the gas-hydrate (GH) petroleum system; to discuss advances, requirements, and suggested practices in GH prospecting and GH deposit characterization; and to review the associated technical, economic, and environmental challenges and uncertainties, which include the following: accurate assessment of producible fractions of the GH resource; development of methods for identifying suitable production targets; sampling of hydrate-bearing sediments (HBS) and sample analysis; analysis and interpretation of geophysical surveys of GH reservoirs; well-testing methods; interpretation of well-testing results; geomechanical and reservoir/well stability concerns; well design, operation, and installation; field operations and extending production beyond sand-dominated GH reservoirs; monitoring production and geomechanical stability; laboratory investigations; fundamental knowledge of hydrate behavior; the economics of commercial gas production from hydrates; and associated environmental concerns. ?? 2011 Society of Petroleum Engineers.

  12. A Computationally Efficient Equation of State for Ternary Gas Hydrate Systems

    NASA Astrophysics Data System (ADS)

    White, M. D.

    2012-12-01

    The potential energy resource of natural gas hydrates held in geologic accumulations, using lower volumetric estimates, is sufficient to meet the world demand for natural gas for nearly eight decades, at current rates of increase. As with other unconventional energy resources, the challenge is to economically produce the natural gas fuel. The gas hydrate challenge is principally technical. Meeting that challenge will require innovation, but more importantly, scientific research to understand the resource and its characteristics in porous media. The thermodynamic complexity of gas hydrate systems makes numerical simulation a particularly attractive research tool for understanding production strategies and experimental observations. Simply stated, producing natural gas from gas hydrate deposits requires releasing CH4 from solid gas hydrate. The conventional way to release CH4 is to dissociate the hydrate by changing the pressure and temperature conditions to those where the hydrate is unstable. Alternatively, the guest-molecule exchange technology releases CH4 by replacing it with more thermodynamically stable molecules (e.g., CO2, N2). This technology has three advantageous: 1) it sequesters greenhouse gas, 2) it potentially releases energy via an exothermic reaction, and 3) it retains the hydraulic and mechanical stability of the hydrate reservoir. Numerical simulation of the production of gas hydrates from geologic deposits requires accounting for coupled processes: multifluid flow, mobile and immobile phase appearances and disappearances, heat transfer, and multicomponent thermodynamics. The ternary gas hydrate system comprises five components (i.e., H2O, CH4, CO2, N2, and salt) and the potential for six phases (i.e., aqueous, nonaqueous liquid, gas, hydrate, ice, and precipitated salt). The equation of state for ternary hydrate systems has three requirements: 1) phase occurrence, 2) phase composition, and 3) phase properties. Numerical simulations that predict

  13. The characteristics of heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

    NASA Astrophysics Data System (ADS)

    Xu, Xing; Wan, Zhifeng; Wang, Xianqing; Sun, Yuefeng; Xia, Bin

    2016-12-01

    Marine heat flow is of great significance for the formation and occurrence of seabed oil, gas and gas hydrate resources. Geothermal gradient is an important parameter in determining the thickness of the hydrate stability zone. The northern slope of the South China Sea is rich in gas hydrate resources. Several borehole drilling attempts were successful in finding hydrates in the Shenhu area, while others were not. The failures demand further study on the distribution regularities of heat flow and its controlling effects on hydrate occurrence. In this study, forty-eight heat flow measurements are analyzed in the Shenhu gas hydrate drilling area, located in the northern South China Sea, together with their relationship to topography, sedimentary environment and tectonic setting. Canyons are well developed in the study area, caused mainly by the development of faults, faster sediment supply and slumping of the Pearl River Estuary since the late Miocene in the northern South China Sea. The heat flow values in grooves, occurring always in fault zones, are higher than those of ridges. Additionally, the heat flow values gradually increase from the inner fan, to the middle fan, to the external fan subfacies. The locations with low heat flow such as ridges, locations away from faults and the middle fan subfacies, are more conducive to gas hydrate occurrence.

  14. Free gas in the regional hydrate stability zone: Implications for hydrate distribution and fracturing behavior

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Dugan, B.

    2010-12-01

    We show that hydrate distribution and fracture genesis in the hydrate stability zone are largely governed by the phase of methane supply. In systems where methane is supplied primarily as free gas, hydrate saturation increases upwards in the hydrate stability zone, and fractures nucleate in the middle of the stability zone where hydrate saturation is highest. In systems where methane is supplied primarily as a dissolved phase in the pore water, hydrate saturation decreases upwards in the stability zone, and fractures nucleate at the base of the stability zone. These interpretations are based on our one-dimensional model that incorporates multiphase flow and free gas within the regional hydrate stability zone (RHSZ). The RHSZ is defined as the interval in which methane hydrate may occur at seawater salinity (3.35% by mass). As hydrate forms and excludes salt from the crystal structure, the porewater salinity increases. Free gas enters the RHSZ when the porewater salinity increases to the value required for three-phase (dissolved methane + gas hydrate + free gas) equilibrium. Our model also incorporates changes to capillary pressure as hydrate forms and occludes the pore system. We model the system until the excess pore pressure exceeds the vertical effective stress in the domain due to capillary effects and pore occlusion, at which point we assume fractures nucleate. We test our model at Hydrate Ridge, where methane supply is dominantly in the gas phase, and show that hydrate saturation increases upwards and fractures nucleate high within the stability zone, eventually allowing gas to vent to the seafloor. We also model Blake Ridge, where methane supply is dominantly in the dissolved phase, and show that hydrate saturation is greatest at the base of the stability zone; fractures nucleate here and in some cases could propagate through the regional hydrate stability zone, allowing methane-charged water to vent to the seafloor. These two systems represent endmembers of

  15. The characteristics of gas hydrates recovered from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Lu, H.; Lorenson, T.D.; Moudrakovski, I.L.; Ripmeester, J.A.; Collett, T.S.; Hunter, R.B.; Ratcliffe, C.I.

    2011-01-01

    Systematic analyses have been carried out on two gas hydrate-bearing sediment core samples, HYPV4, which was preserved by CH4 gas pressurization, and HYLN7, which was preserved in liquid-nitrogen, recovered from the BPXA-DOE-USGS Mount Elbert Stratigraphic Test Well. Gas hydrate in the studied core samples was found by observation to have developed in sediment pores, and the distribution of hydrate saturation in the cores imply that gas hydrate had experienced stepwise dissociation before it was stabilized by either liquid nitrogen or pressurizing gas. The gas hydrates were determined to be structure Type I hydrate with hydration numbers of approximately 6.1 by instrumentation methods such as powder X-ray diffraction, Raman spectroscopy and solid state 13C NMR. The hydrate gas composition was predominantly methane, and isotopic analysis showed that the methane was of thermogenic origin (mean ??13C=-48.6??? and ??D=-248??? for sample HYLN7). Isotopic analysis of methane from sample HYPV4 revealed secondary hydrate formation from the pressurizing methane gas during storage. ?? 2010 Elsevier Ltd.

  16. Scientific Objectives of the Gulf of Mexico Gas Hydrate JIP Leg II Drilling

    SciTech Connect

    Jones, E.; Latham, T.; McConnell, D.; Frye, M.; Hunt, J.; Shedd, W.; Shelander, D.; Boswell, R.M.; Rose, K.K.; Ruppel, C.; Hutchinson, D.; Collett, T.; Dugan, B.; Wood, W.

    2008-05-01

    The Gulf of Mexico Methane Hydrate Joint Industry Project (JIP) has been performing research on marine gas hydrates since 2001 and is sponsored by both the JIP members and the U.S. Department of Energy. In 2005, the JIP drilled the Atwater Valley and Keathley Canyon exploration blocks in the Gulf of Mexico to acquire downhole logs and recover cores in silt- and clay-dominated sediments interpreted to contain gas hydrate based on analysis of existing 3-D seismic data prior to drilling. The new 2007-2009 phase of logging and coring, which is described in this paper, will concentrate on gas hydrate-bearing sands in the Alaminos Canyon, Green Canyon, and Walker Ridge protraction areas. Locations were selected to target higher permeability, coarser-grained lithologies (e.g., sands) that have the potential for hosting high saturations of gas hydrate and to assist the U.S. Minerals Management Service with its assessment of gas hydrate resources in the Gulf of Mexico. This paper discusses the scientific objectives for drilling during the upcoming campaign and presents the results from analyzing existing seismic and well log data as part of the site selection process. Alaminos Canyon 818 has the most complete data set of the selected blocks, with both seismic data and comprehensive downhole log data consistent with the occurrence of gas hydrate-bearing sands. Preliminary analyses suggest that the Frio sandstone just above the base of the gas hydrate stability zone may have up to 80% of the available sediment pore space occupied by gas hydrate. The proposed sites in the Green Canyon and Walker Ridge areas are also interpreted to have gas hydrate-bearing sands near the base of the gas hydrate stability zone, but the choice of specific drill sites is not yet complete. The Green Canyon site coincides with a 4-way closure within a Pleistocene sand unit in an area of strong gas flux just south of the Sigsbee Escarpment. The Walker Ridge site is characterized by a sand

  17. Downhole well log and core montages from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Collett, T.S.; Lewis, R.E.; Winters, W.J.; Lee, M.W.; Rose, K.K.; Boswell, R.M.

    2011-01-01

    The BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well was an integral part of an ongoing project to determine the future energy resource potential of gas hydrates on the Alaska North Slope. As part of this effort, the Mount Elbert well included an advanced downhole geophysical logging program. Because gas hydrate is unstable at ground surface pressure and temperature conditions, a major emphasis was placed on the downhole-logging program to determine the occurrence of gas hydrates and the in-situ physical properties of the sediments. In support of this effort, well-log and core data montages have been compiled which include downhole log and core-data obtained from the gas-hydrate-bearing sedimentary section in the Mount Elbert well. Also shown are numerous reservoir parameters, including gas-hydrate saturation and sediment porosity log traces calculated from available downhole well log and core data. ?? 2010.

  18. Preface to the special issue on gas hydrate drilling in the Eastern Nankai Trough

    USGS Publications Warehouse

    Yamamoto, Koji; Ruppel, Carolyn D.

    2015-01-01

    Methane hydrate traps enormous amounts of methane in frozen deposits in continental margin sediments, and these deposits have long been targeted for studies investigating their potential as an energy resource. As a concentrated form of methane that occurs at shallower depths than conventional and most unconventional gas reservoirs, methane hydrates could be a readily accessible source of hydrocarbons for countries hosting deposits within their Exclusive Economic Zones. Japan is one such country, and since 2001 the Research Consortium for Methane Hydrate Resources in Japan (referred to as MH21) has conducted laboratory, modeling, and field-based programs to study methane hydrates as an energy resource. The MH21 consortium is funded by the Japanese Ministry of Trade and Industry (METI) and led by the Japan Oil, Gas and Metals National Oil Corporation (JOGMEC) and the National Institute of Advanced Industrial Science and Technology (AIST).

  19. Simulation of natural gas production from submarine gas hydrate deposits combined with carbon dioxide storage

    NASA Astrophysics Data System (ADS)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2013-04-01

    The recovery of methane from gas hydrate layers that have been detected in several submarine sediments and permafrost regions around the world so far is considered to be a promising measure to overcome future shortages in natural gas as fuel or raw material for chemical syntheses. Being aware that natural gas resources that can be exploited with conventional technologies are limited, research is going on to open up new sources and develop technologies to produce methane and other energy carriers. Thus various research programs have started since the early 1990s in Japan, USA, Canada, South Korea, India, China and Germany to investigate hydrate deposits and develop technologies to destabilize the hydrates and obtain the pure gas. In recent years, intensive research has focussed on the capture and storage of carbon dioxide from combustion processes to reduce climate change. While different natural or manmade reservoirs like deep aquifers, exhausted oil and gas deposits or other geological formations are considered to store gaseous or liquid carbon dioxide, the storage of carbon dioxide as hydrate in former methane hydrate fields is another promising alternative. Due to beneficial stability conditions, methane recovery may be well combined with CO2 storage in form of hydrates. This has been shown in several laboratory tests and simulations - technical field tests are still in preparation. Within the scope of the German research project »SUGAR«, different technological approaches are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical effects are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs like CMG STARS and COMSOL Multiphysics. New simulations based on field data have been carried out. The studies focus on the evaluation of the gas production

  20. Geochemistry of a naturally occurring massive marine gas hydrate

    USGS Publications Warehouse

    Kvenvolden, K.A.; Claypool, G.E.; Threlkeld, C.N.; Dendy, Sloan E.

    1984-01-01

    During Deep Sea Drilling Project (DSDP) Leg 84 a core 1 m long and 6 cm in diameter of massive gas hydrate was unexpectedly recovered at Site 570 in upper slope sediment of the Middle America Trench offshore of Guatemala. This core contained only 5-7% sediment, the remainder being the solid hydrate composed of gas and water. Samples of the gas hydrate were decomposed under controlled conditions in a closed container maintained at 4??C. Gas pressure increased and asymptotically approached the equilibrium decomposition pressure for an ideal methane hydrate, CH4.5-3/4H2O, of 3930 kPa and approached to this pressure after each time gas was released, until the gas hydrate was completely decomposed. The gas evolved during hydrate decomposition was 99.4% methane, ???0.2% ethane, and ???0.4% CO2. Hydrocarbons from propane to heptane were also present, but in concentrations of less than 100 p.p.m. The carbon-isotopic composition of methane was -41 to -44 permil(( 0 00), relative to PDB standard. The observed volumetric methane/water ratio was 64 or 67, which indicates that before it was stored and analyzed, the gas hydrate probably had lost methane. The sample material used in the experiments was likely a mixture of methane hydrate and water ice. Formation of this massive gas hydrate probably involved the following processes: (i) upward migration of gas and its accumulation in a zone where conditions favored the growth of gas hydrates, (ii) continued, unusually rapid biological generation of methane, and (iii) release of gas from water solution as pressure decreased due to sea level lowering and tectonic uplift. ?? 1984.

  1. Gas hydrate contribution to Late Permian global warming

    NASA Astrophysics Data System (ADS)

    Majorowicz, J.; Grasby, S. E.; Safanda, J.; Beauchamp, B.

    2014-05-01

    Rapid gas hydrate release (the “clathrate gun” hypothesis) has been invoked as a cause for the rapid global warming and associated negative carbon isotope excursion observed during the Latest Permian Extinction (LPE). We modeled the stability of gas hydrates through a warming Middle to Late Permian world, considering three settings for methane reservoirs: 1) terrestrial hydrates, 2) hydrates on exposed continental shelves during glacial sea level drop, and 3) hydrates in deep marine settings. Model results show that terrestrial hydrates would rapidly destabilize over ∼400 ky after deglaciation for moderate heatflow (40 mW/m2), and more rapidly for higher heat flow values. Exposed continental shelves would lose hydrates even more rapidly, after being flooded due to loss of ice storage on land. These two major hydrate reservoirs would thus have destabilized during the Middle to Late Permian climate warming, well prior to the LPE event. However, they may have contributed to the >2‰ negative C-isotopic shift during the late Middle Permian. Deep marine hydrates would have remained stable until LPE time. Rapid warming of deep marine waters during this time could have triggered destabilization of this reservoir, however given the configuration of one super continent, Pangea, hydrate bearing continental slopes would have been less extensive than modern day. This suggests that any potential gas hydrate release would have had only a minor contributing impact to the runaway greenhouse during the Latest Permian extinction.

  2. Simulation of submarine gas hydrate deposits as a sustainable energy source and CO2 storage

    NASA Astrophysics Data System (ADS)

    Janicki, G.; Hennig, T.; Schlüter, S.; Deerberg, G.

    2012-04-01

    Being aware that conventionally exploitable natural gas resources are limited, research concentrates on the development of new technologies for the extraction of methane from gas hydrate deposits in subsea sediments. The quantity of methane stored in hydrate form is considered to be a promising means to overcome future shortages in energy resources. In combination with storing carbon dioxide (CO2) as hydrates in the deposits chances for sustainable energy supply systems are given. The combustion of hydrate-based natural gas can contribute to the energy supply, but the coupled CO2 emissions cause climate change effects. At present, the possible options to capture and subsequently store CO2 (CCS-Technology) become of particular interest. To develop a sustainable hydrate-based energy supply system, the production of natural gas from hydrate deposits has to be coupled with the storage of CO2. Hence, the simultaneous storage of CO2 in hydrate deposits has to be developed. Decomposition of methane hydrate in combination with CO2 sequestration appears to be promising because CO2 hydrate is stable within a wider range of pressure and temperature than methane hydrate. As methane hydrate provides structural integrity and stability in its natural formation, incorporating CO2 hydrate as substitute for methane hydrate will help to preserve the natural sediments' stability. Regarding the technological implementation, many problems have to be overcome. Especially heat and mass transfer in the deposits are limiting factors causing very long process times. Within the scope of the German research project »SUGAR«, different technological approaches are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical effects are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs like

  3. Evaluation of Gas Production Potential of Hydrate Deposits in Alaska North Slope using Reservoir Simulations

    NASA Astrophysics Data System (ADS)

    Nandanwar, M.; Anderson, B. J.

    2015-12-01

    Over the past few decades, the recognition of the importance of gas hydrates as a potential energy resource has led to more and more exploration of gas hydrate as unconventional source of energy. In 2002, U.S. Geological Survey (USGS) started an assessment to conduct a geology-based analysis of the occurrences of gas hydrates within northern Alaska. As a result of this assessment, many potential gas hydrate prospects were identified in the eastern National Petroleum Reserve Alaska (NPRA) region of Alaska North Slope (ANS) with total gas in-place of about 2 trillion cubic feet. In absence of any field test, reservoir simulation is a powerful tool to predict the behavior of the hydrate reservoir and the amount of gas that can be technically recovered using best suitable gas recovery technique. This work focuses on the advanced evaluation of the gas production potential of hydrate accumulation in Sunlight Peak - one of the promising hydrate fields in eastern NPRA region using reservoir simulations approach, as a part of the USGS gas hydrate development Life Cycle Assessment program. The main objective of this work is to develop a field scale reservoir model that fully describes the production design and the response of hydrate field. Due to the insufficient data available for this field, the distribution of the reservoir properties (such as porosity, permeability and hydrate saturation) are approximated by correlating the data from Mount Elbert hydrate field to obtain a fully heterogeneous 3D reservoir model. CMG STARS is used as a simulation tool to model multiphase, multicomponent fluid flow and heat transfer in which an equilibrium model of hydrate dissociation was used. Production of the gas from the reservoir is carried out for a period of 30 years using depressurization gas recovery technique. The results in terms of gas and water rate profiles are obtained and the response of the reservoir to pressure and temperature changes due to depressurization and hydrate

  4. Geophysical Methodologies for the Characterisation of Gas Hydrate Sediments

    NASA Astrophysics Data System (ADS)

    Lovell, M.; Jackson, P.; Gunn, D.; Rochelle, C.; Bateman, K.; Nelder, V.; Culshaw, M.; Rees, J.; Francis, T.; Roberts, J.; Schultheiss, P.

    2001-12-01

    The study of natural gas hydrate cores in the laboratory is currently limited by their instability at ambient conditions. Proposals to sample hydrates using pressure coring techniques and sample transfer chambers on-board ship are, however, in place and technical developments to enable these are well advanced (c.f. the HYACINTH project and ODP Leg 204). There is, however, a need to try to characterise the nature and extent of any gas hydrate within the pressurised sample prior to depressurising, opening and subsampling. The ability to geophysically characterise gas hydrates remotely while still in the pressurised core barrel may provide a route to detailing their physical extent and nature. With this objective, experiments to manufacture a range of synthetic gas hydrate morphologies in a range of sediments in the laboratory are in progress. To date we have succeeded in manufacturing a range of both pure and sediment-hosted CO2 hydrates. Continuing experiments are developing a range of geometrical and internal structures and fabrics (from massive to disseminated) using different sediment-hosts. These generic hydrate groups will provide a basis for non-invasive geophysical characterisation of hydrate morphologies. From these results protocols will be established to guide the geophysical logging of natural sediment-hydrate core maintained under pressure in lab transfer chambers on board the drillship, using the hyperbaric Geotek Core Logger. This will enable the characterisation and classification of hydrates sampled during ODP Leg 204 (and during subsequent hydrate sampling operations not restricted to ODP). While new insight will be gained into geophysical modelling of hydrate behaviour, it will also guide the development of sampling programs, prior to depressurising and initiating dissociation. This will allow detailed planning of shipboard scientific work utilising these rare and precious samples. This new knowledge will enhance geophysical survey data, better

  5. Sedimentological Properties of Natural Gas Hydrates-Bearing Sands in the Nankai Trough and Mallik Areas

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Tsuji, T.; Waseda, A.

    2009-12-01

    sands should have permeability of 1 x 10-15 to 5 x 10-15 m2 (1 to 5 millidarcies). Most of gas hydrates fill the intergranular pore systems of sandy layers, which are derived from the sedimentary facies such as channels and crevasse splay/levee deposits. It is remarked that those sandy strata are usually composed of arenite sands with matrix-free intergranular pore systems. Gas hydrates are less frequently found in fine-grained sediments such as siltstone and mudstone from overbank deposits. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. This appears to be a similar mode for conventional oil and gas accumulations, and this knowledge is important to predicting the location of other hydrate deposits and their eventual energy resource. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

  6. In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Lee, M.W.; Collett, T.S.

    2011-01-01

    In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

  7. Entrapment of Hydrate-coated Gas Bubbles into Oil and Separation of Gas and Hydrate-film; Seafloor Experiments with ROV

    NASA Astrophysics Data System (ADS)

    Hiruta, A.; Matsumoto, R.

    2015-12-01

    We trapped gas bubbles emitted from the seafloor into oil-containing collector and observed an unique phenomena. Gas hydrate formation needs water for the crystal lattice; however, gas hydrates in some areas are associated with hydrophobic crude oil or asphalt. In order to understand gas hydrate growth in oil-bearing sediments, an experiment with cooking oil was made at gas hydrate stability condition. We collected venting gas bubbles into a collector with canola oil during ROV survey at a gas hydrate area in the eastern margin of the Sea of Japan. When the gas bubbles were trapped into collector with oil, gas phase appeared above the oil and gas hydrates, between oil and gas phase. At this study area within gas hydrate stability condition, control experiment with oil-free collector suggested that gas bubbles emitted from the seafloor were quickly covered with gas hydrate film. Therefore it is improbable that gas bubbles entered into the oil phase before hydrate skin formation. After the gas phase formation in oil-containing collector, the ROV floated outside of hydrate stability condition for gas hydrate dissociation and re-dived to the venting site. During the re-dive within hydrate stability condition, gas hydrate was not formed. The result suggests that moisture in the oil is not enough for hydrate formation. Therefore gas hydrates that appeared at the oil/gas phase boundary were already formed before bubbles enter into the oil. Hydrate film is the only possible origin. This observation suggests that hydrate film coating gas hydrate was broken at the sea water/oil boundary or inside oil. Further experiments may contribute for revealing kinetics of hydrate film and formation. This work was a part of METI (Ministry of Economy, Trade and Industry)'s project entitled "FY2014 Promoting research and development of methane hydrate". We also appreciate support of AIST (National Institute of Advanced Industrial Science and Technology).

  8. Dynamics of the gas hydrate system off Svalbard

    NASA Astrophysics Data System (ADS)

    Berndt, Christian; Feseker, Tomas; Treude, Tina; Krastel, Sebastian; Liebetrau, Volker; Niemann, Helge; Bertics, Victoria; Dumke, Ines; Dünnbier, Karolin; Ferre, Benedicte; Graves, Carolyn; Gross, Felix; Hissmann, Karen; Hühnerbach, Veit; Krause, Stefan; Lieser, Kathrin; Schauer, Jürgen; Steinle, Lea

    2013-04-01

    Marine methane hydrate is an ice-like substance stable at high-pressure and low temperature found frequently in continental margins. Since discovery of a large number of gas flares between 380 and 400 m water depth at the landward termination of the gas hydrate stability zone off Svalbard, there is concern that warming bottom waters have already started to melt large amounts of marine gas hydrate and may possibly accelerate global warming. The location of gas flares observed in PARASOUND data, geochemical anomalies in sediment cores, and anomalies in heat flow profiles suggest that hydrates play a role in the observed seepage of gas. However, the observation of thick carbonate crusts during manned submersible dives and their subsequent dating suggest that seepage off Svalbard has been ongoing for at least several hundred years and that decadal scale warming of the West Svalbard Current is at most of minor importance for the bulk of the observed seepage. Thus, the seeps off Svalbard do not necessarily represent the beginning of large-scale hydrate dissociation in the Arctic. Instead, it is likely that seasonal bottom water temperature fluctuations of 1-2°C cause periodic gas hydrate formation and dissociation, which focuses seepage at the observed gas flare depth. The results show that hydrate is highly sensitive to bottom water temperature changes and that bottom water warming will affect the stability of any large hydrate accumulations at the seabed on a short time scale.

  9. Gas hydrates on the Atlantic Continental Margin of the United States - controls on concentration

    SciTech Connect

    Dillon, W.P.; Fehlhaber, K.; Coleman, D.F. ); Lee, M.W. )

    1993-01-01

    Large volumes of gas hydrates exist within ocean-floor deposits at water depths exceeding about 300 to 500 m. They cement a surface layer of sediments as much as about 1,000 m thick, limited at its base by increasing temperature. Gas hydrates are identified by drilled samples and by their characteristic responses in seismic reflection profiles. These seismic responses include, at the base of the hydrate-cemented surface layer, a marked velocity decrease and a sea-floor-paralleling reflection (known as the bottom-simulating reflection, or BSR), and, within the hydrate-cemented layer, a reduction in amplitude of seismic reflections (known as blanking), which is apparently caused by cementation of strata. By using seismic-reflection data we have mapped the volume of hydrate and thickness of the hydrate-cemented layer off the US East Coast. The sources of gas at these concentrations are probably bacterial generation of methane at the locations of rapid deposition, and possibly the migration of deep, thermogenic gap up faults near diapirs. The thickness of the gas-hydrate layer decreases markedly at landslide scars, possibly due to break-down of hydrate resulting from pressure reduction caused by removal of sediment by the slide. Gas traps appear to exist where a seal is formed by the gas-hydrate-cemented layer. Such traps are observed (1) where the sea floor forms a dome, and therefore the bottom-paralleling, hydrate-cemented layer also forms a dome; (2) above diapirs, where the greater thermal conductivity of salt creates a warm spot and salt ions act as antifreeze, both effects resulting in a local shallowing of the base of the hydrate; and (3) at locations where strata dip relative to the sea floor, and the updip regions of porous strata are sealed by the gas-hydrate-cemented layer to form a trap. In such situations the gas in the hydrate-sealed trap, as well as the gas that forms the hydrate, may become a resource. 32 refs., 19 figs.

  10. Surfactant process for promoting gas hydrate formation and application of the same

    DOEpatents

    Rogers, Rudy E.; Zhong, Yu

    2002-01-01

    This invention relates to a method of storing gas using gas hydrates comprising forming gas hydrates in the presence of a water-surfactant solution that comprises water and surfactant. The addition of minor amounts of surfactant increases the gas hydrate formation rate, increases packing density of the solid hydrate mass and simplifies the formation-storage-decomposition process of gas hydrates. The minor amounts of surfactant also enhance the potential of gas hydrates for industrial storage applications.

  11. Observations of gas hydrates in marine sediments, offshore northern California

    USGS Publications Warehouse

    Brooks, J.M.; Field, M.E.; Kennicutt, M.C.

    1991-01-01

    Biogenic gas hydrates were recovered in shallow cores (< 6 m deep) from the Eel River basin in offshore northern California between 40??38??? and 40??56???N. The gas hydrates contained primarily methane (??13C = -57.6 to -69.1???) and occurred as dispersed crystals, small (2-20 mm) nodules, and layered bands within the sediment. These hydrates, recovered in sediment at water depths between 510 and 642 m, coincide nearly, but not exactly, with areas showing bottom-simulating reflectors (BSRs) on seismic-reflection records. This study confirms indirect geophysical and geologic observations that gas hydrates are present north of the Mendocino Fracture Zone in sediment of the Eel River basin but probably are absent to the south in the Point Arena basin. This discovery extends the confirmed sites of gas hydrates in the eastern Pacific region beyond the Peruvian and Central American margins to the northern California margin. ?? 1991.

  12. Rapid gas hydrate formation processes: Will they work?

    DOE PAGES

    Brown, Thomas D.; Taylor, Charles E.; Bernardo, Mark P.

    2010-06-07

    Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated with natural and synthetic hydrates studies conducted in the laboratory. Numerous experiments were conducted with various high-pressure cells equipped with instrumentation to study rapid and continuous hydrate formation. The cells ranged in size from 100 mL for screening studies to proof-of-concept studies with NETL’s 15-Liter Hydrate Cell. The results from this work demonstrate that the rapid and continuousmore » formation of methane hydrate is possible at predetermined temperatures and pressures within the stability zone of a Methane Hydrate Stability Curve.« less

  13. Rapid gas hydrate formation processes: Will they work?

    SciTech Connect

    Brown, Thomas D.; Taylor, Charles E.; Bernardo, Mark P.

    2010-06-07

    Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated with natural and synthetic hydrates studies conducted in the laboratory. Numerous experiments were conducted with various high-pressure cells equipped with instrumentation to study rapid and continuous hydrate formation. The cells ranged in size from 100 mL for screening studies to proof-of-concept studies with NETL’s 15-Liter Hydrate Cell. The results from this work demonstrate that the rapid and continuous formation of methane hydrate is possible at predetermined temperatures and pressures within the stability zone of a Methane Hydrate Stability Curve.

  14. Gas hydrate formation rates from dissolved-phase methane in porous laboratory specimens

    USGS Publications Warehouse

    Waite, William F.; Spangenberg, E.K.

    2013-01-01

    Marine sands highly saturated with gas hydrates are potential energy resources, likely forming from methane dissolved in pore water. Laboratory fabrication of gas hydrate-bearing sands formed from dissolved-phase methane usually requires 1–2 months to attain the high hydrate saturations characteristic of naturally occurring energy resource targets. A series of gas hydrate formation tests, in which methane-supersaturated water circulates through 100, 240, and 200,000 cm3 vessels containing glass beads or unconsolidated sand, show that the rate-limiting step is dissolving gaseous-phase methane into the circulating water to form methane-supersaturated fluid. This implies that laboratory and natural hydrate formation rates are primarily limited by methane availability. Developing effective techniques for dissolving gaseous methane into water will increase formation rates above our observed (1 ± 0.5) × 10−7 mol of methane consumed for hydrate formation per minute per cubic centimeter of pore space, which corresponds to a hydrate saturation increase of 2 ± 1% per day, regardless of specimen size.

  15. Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Overview of scientific and technical program

    USGS Publications Warehouse

    Hunter, R.B.; Collett, T.S.; Boswell, R.; Anderson, B.J.; Digert, S.A.; Pospisil, G.; Baker, R.; Weeks, M.

    2011-01-01

    The Mount Elbert Gas Hydrate Stratigraphic Test Well was drilled within the Alaska North Slope (ANS) Milne Point Unit (MPU) from February 3 to 19, 2007. The well was conducted as part of a Cooperative Research Agreement (CRA) project co-sponsored since 2001 by BP Exploration (Alaska), Inc. (BPXA) and the U.S. Department of Energy (DOE) in collaboration with the U.S. Geological Survey (USGS) to help determine whether ANS gas hydrate can become a technically and commercially viable gas resource. Early in the effort, regional reservoir characterization and reservoir simulation modeling studies indicated that up to 0.34 trillion cubic meters (tcm; 12 trillion cubic feet, tcf) gas may be technically recoverable from 0.92 tcm (33 tcf) gas-in-place within the Eileen gas hydrate accumulation near industry infrastructure within ANS MPU, Prudhoe Bay Unit (PBU), and Kuparuk River Unit (KRU) areas. To further constrain these estimates and to enable the selection of a test site for further data acquisition, the USGS reprocessed and interpreted MPU 3D seismic data provided by BPXA to delineate 14 prospects containing significant highly-saturated gas hydrate-bearing sand reservoirs. The "Mount Elbert" site was selected to drill a stratigraphic test well to acquire a full suite of wireline log, core, and formation pressure test data. Drilling results and data interpretation confirmed pre-drill predictions and thus increased confidence in both the prospect interpretation methods and in the wider ANS gas hydrate resource estimates. The interpreted data from the Mount Elbert well provide insight into and reduce uncertainty of key gas hydrate-bearing reservoir properties, enable further refinement and validation of the numerical simulation of the production potential of both MPU and broader ANS gas hydrate resources, and help determine viability of potential field sites for future extended term production testing. Drilling and data acquisition operations demonstrated that gas hydrate

  16. Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

    2014-12-01

    The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

  17. The role of water in gas hydrate dissociation

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product.

  18. Fundamental challenges to methane recovery from gas hydrates

    USGS Publications Warehouse

    Servio, P.; Eaton, M.W.; Mahajan, D.; Winters, W.J.

    2005-01-01

    The fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources, are presented. To induce dissociation of gas hydrate prior to methane recovery, two potential methods are typically considered. Because thermal stimulation requires a large energy input, it is less economically feasible than depressurization. The new data will allow the study of the effect of pressure, temperature, diffusion, porosity, tortuosity, composition of gas and water, and porous media on gas-hydrate production. These data also will allow one to improve existing models related to the stability and dissociation of sea floor hydrates. The reproducible kinetic data from the planned runs together with sediment properties will aid in developing a process to economically recover methane from a potential untapped hydrate source. The availability of plentiful methane will allow economical and large-scale production of methane-derived clean fuels to help avert future energy crises.

  19. Gas sources migration paths, and seafloor seepage associated with marine gas-hydrates

    SciTech Connect

    Paull, C.K.

    1995-12-31

    Some continental margin sediments, like those on the Blake Ridge, are observed to have {ge}5% of their pore space occupied by gas hydrates. In situ microbial methane production is insufficient to form gas hydrate in these amounts, thus fluid migration and other gas-concentrating mechanisms are required to develop these gas hydrate accumulations. Several potential mechanisms exist. Some gas may be provided from deeper sediments by compaction and bubble distillation. Gas hydrate gas may be slowly recycled at the base of the gas-hydrate stability (BGHS) zone because of progressive subsidence and burial of the continental rise. Formerly stable hydrates will break down, and the methane released will migrate upward, re-enter the gas hydrate stability zone, and reform gas hydrate. Recycled gas will augment the gas produced in situ. Lateral gas migration may be focused along a relatively permeable conduit immediately below the BGHS. Gas may also migrate upward along faults or other permeable conduits and provide additional methane to form more gas-hydrate in sediments above the BGHS. Methane may escape onto the seafloor from faults that penetrate to the BGHS. Models of fluid movement will be assessed during ODP Leg 163.

  20. Controls on the physical properties of gas-hydrate-bearing sediments because of the interaction between gas hydrate and porous media

    USGS Publications Warehouse

    Lee, Myung W.; Collett, Timothy S.

    2005-01-01

    Physical properties of gas-hydrate-bearing sediments depend on the pore-scale interaction between gas hydrate and porous media as well as the amount of gas hydrate present. Well log measurements such as proton nuclear magnetic resonance (NMR) relaxation and electromagnetic propagation tool (EPT) techniques depend primarily on the bulk volume of gas hydrate in the pore space irrespective of the pore-scale interaction. However, elastic velocities or permeability depend on how gas hydrate is distributed in the pore space as well as the amount of gas hydrate. Gas-hydrate saturations estimated from NMR and EPT measurements are free of adjustable parameters; thus, the estimations are unbiased estimates of gas hydrate if the measurement is accurate. However, the amount of gas hydrate estimated from elastic velocities or electrical resistivities depends on many adjustable parameters and models related to the interaction of gas hydrate and porous media, so these estimates are model dependent and biased. NMR, EPT, elastic-wave velocity, electrical resistivity, and permeability measurements acquired in the Mallik 5L-38 well in the Mackenzie Delta, Canada, show that all of the well log evaluation techniques considered provide comparable gas-hydrate saturations in clean (low shale content) sandstone intervals with high gas-hydrate saturations. However, in shaly intervals, estimates from log measurement depending on the pore-scale interaction between gas hydrate and host sediments are higher than those estimates from measurements depending on the bulk volume of gas hydrate.

  1. The relations between natural gas hydrate distribution and structure on Muli basin Qinghai province

    NASA Astrophysics Data System (ADS)

    Yu, C.; Li, Y.; Lu, Z.; Luo, S.; Qu, C.; Tan, S.; Zhang, P.

    2014-12-01

    The Muli area is located in a depression area which between middle Qilian and south Qilian tectonic elements. The natural gas hydrate stratum belongs the Jurassic series coal formation stratum, the main lithological character clamps the purple mudstone, the siltstone, the fine grain sandstone and the black charcoal mudstone for the green gray. The plutonic metamorphism is primarily deterioration function of the Muli area coal, is advantageous in forming the coal-bed gas. Cretaceous system, the Paleogene System and Neogene System mainly include the fine grain red clastic rock and clay stone. The distribution of Quaternary is widespread. The ice water - proluvial and glacier deposit are primarily depositional mode. The Qilian Montanan Muli permafrost area has the good gas source condition (Youhai Zhu 2006) and rich water resources. It is advantage to forming the natural gas hydrate. The natural gas hydrate is one kind of new latent energy, widely distributes in the mainland marginal sea bottom settlings and land permanent tundra. Through researching the area the structure ,the deposition carries on the analysis and responds the characteristic analysis simulation in the rock physics analysis and the seismic in the foundation, and then the reflected seismic data carried by tectonic analysis processing and the AVO characteristic analysis processing reveal that the research area existence natural gas hydrate (already by drilling confirmation) and the natural gas hydrate distribution and the structure relations is extremely close. In the structure development area, the fault and the crevasse crack growing, the natural gas hydrate distribution characteristic is obvious (this is also confirmed the storing space of natural gas hydrate in this area is mainly crevasse crack). This conclusion also agree with the actual drilling result. The research prove that the distribution of natural gas hydrate in this area is mainly controlled by structure control. The possibility of fault

  2. New hydrate formation methods in a liquid-gas medium

    NASA Astrophysics Data System (ADS)

    Chernov, A. A.; Pil’Nik, A. A.; Elistratov, D. S.; Mezentsev, I. V.; Meleshkin, A. V.; Bartashevich, M. V.; Vlasenko, M. G.

    2017-01-01

    Conceptually new methods of hydrate formation are proposed. The first one is based on the shock wave impact on a water-bubble medium. It is shown that the hydrate formation rate in this process is typically very high. A gas hydrate of carbon dioxide was produced. The process was experimentally studied using various initial conditions, as well as different external action magnitudes. The obtained experimental data are in good agreement with the proposed model. Other methods are based on the process of boiling liquefied gas in an enclosed volume of water (explosive boiling of a hydrating agent and the organization of cyclic boiling-condensation process). The key features of the methods are the high hydrate formation rate combined with a comparatively low power consumption leading to a great expected efficiency of the technologies based on them. The set of experiments was carried out. Gas hydrates of refrigerant R134a, carbon dioxide and propane were produced. The investigation of decomposition of a generated gas hydrate sample was made. The criteria of intensification of the hydrate formation process are formulated.

  3. New hydrate formation methods in a liquid-gas medium

    PubMed Central

    Chernov, A. A.; Pil’nik, A. A.; Elistratov, D. S.; Mezentsev, I. V.; Meleshkin, A. V.; Bartashevich, M. V.; Vlasenko, M. G.

    2017-01-01

    Conceptually new methods of hydrate formation are proposed. The first one is based on the shock wave impact on a water-bubble medium. It is shown that the hydrate formation rate in this process is typically very high. A gas hydrate of carbon dioxide was produced. The process was experimentally studied using various initial conditions, as well as different external action magnitudes. The obtained experimental data are in good agreement with the proposed model. Other methods are based on the process of boiling liquefied gas in an enclosed volume of water (explosive boiling of a hydrating agent and the organization of cyclic boiling-condensation process). The key features of the methods are the high hydrate formation rate combined with a comparatively low power consumption leading to a great expected efficiency of the technologies based on them. The set of experiments was carried out. Gas hydrates of refrigerant R134a, carbon dioxide and propane were produced. The investigation of decomposition of a generated gas hydrate sample was made. The criteria of intensification of the hydrate formation process are formulated. PMID:28098194

  4. New hydrate formation methods in a liquid-gas medium.

    PubMed

    Chernov, A A; Pil'nik, A A; Elistratov, D S; Mezentsev, I V; Meleshkin, A V; Bartashevich, M V; Vlasenko, M G

    2017-01-18

    Conceptually new methods of hydrate formation are proposed. The first one is based on the shock wave impact on a water-bubble medium. It is shown that the hydrate formation rate in this process is typically very high. A gas hydrate of carbon dioxide was produced. The process was experimentally studied using various initial conditions, as well as different external action magnitudes. The obtained experimental data are in good agreement with the proposed model. Other methods are based on the process of boiling liquefied gas in an enclosed volume of water (explosive boiling of a hydrating agent and the organization of cyclic boiling-condensation process). The key features of the methods are the high hydrate formation rate combined with a comparatively low power consumption leading to a great expected efficiency of the technologies based on them. The set of experiments was carried out. Gas hydrates of refrigerant R134a, carbon dioxide and propane were produced. The investigation of decomposition of a generated gas hydrate sample was made. The criteria of intensification of the hydrate formation process are formulated.

  5. Effect of permafrost properties on gas hydrate petroleum system in the Qilian Mountains, Qinghai, Northwest China.

    PubMed

    Wang, Pingkang; Zhang, Xuhui; Zhu, Youhai; Li, Bing; Huang, Xia; Pang, Shouji; Zhang, Shuai; Lu, Cheng; Xiao, Rui

    2014-12-01

    The gas hydrate petroleum system in the permafrost of the Qilian Mountains, which exists as an epigenetic hydrocarbon reservoir above a deep-seated hydrocarbon reservoir, has been dynamic since the end of the Late Pleistocene because of climate change. The permafrost limits the occurrence of gas hydrate reservoirs by changing the pressure-temperature (P-T) conditions, and it affects the migration of the underlying hydrocarbon gas because of its strong sealing ability. In this study, we reconstructed the permafrost structure of the Qilian Mountains using a combination of methods and measured methane permeability in ice-bearing sediment permafrost. A relationship between the ice saturation of permafrost and methane permeability was established, which permitted the quantitative evaluation of the sealing ability of permafrost with regard to methane migration. The test results showed that when ice saturation is >80%, methane gas can be completely sealed within the permafrost. Based on the permafrost properties and genesis of shallow gas, we suggest that a shallow "gas pool" occurred in the gas hydrate petroleum system in the Qilian Mountains. Its formation was related to a metastable gas hydrate reservoir controlled by the P-T conditions, sealing ability of the permafrost, fault system, and climatic warming. From an energy perspective, the increasing volume of the gas pool means that it will likely become a shallow gas resource available for exploitation; however, for the environment, the gas pool is an underground "time bomb" that is a potential source of greenhouse gas.

  6. GAS METHANE HYDRATES-RESEARCH STATUS, ANNOTATED BIBLIOGRAPHY, AND ENERGY IMPLICATIONS

    SciTech Connect

    James Sorensen; Jaroslav Solc; Bethany Bolles

    2000-07-01

    The objective of this task as originally conceived was to compile an assessment of methane hydrate deposits in Alaska from available sources and to make a very preliminary evaluation of the technical and economic feasibility of producing methane from these deposits for remote power generation. Gas hydrates have recently become a target of increased scientific investigation both from the standpoint of their resource potential to the natural gas and oil industries and of their positive and negative implications for the global environment After we performed an extensive literature review and consulted with representatives of the U.S. Geological Survey (USGS), Canadian Geological Survey, and several oil companies, it became evident that, at the current stage of gas hydrate research, the available information on methane hydrates in Alaska does not provide sufficient grounds for reaching conclusions concerning their use for energy production. Hence, the original goals of this task could not be met, and the focus was changed to the compilation and review of published documents to serve as a baseline for possible future research at the Energy & Environmental Research Center (EERC). An extensive annotated bibliography of gas hydrate publications has been completed. The EERC will reassess its future research opportunities on methane hydrates to determine where significant initial contributions could be made within the scope of limited available resources.

  7. Brookian sequence well log correlation sections and occurrence of gas hydrates, north-central North Slope, Alaska

    USGS Publications Warehouse

    Lewis, Kristen A.; Collett, Timothy S.

    2013-01-01

    Gas hydrates are naturally occurring crystalline, ice-like substances that consist of natural gas molecules trapped in a solid-water lattice. Because of the compact nature of their structure, hydrates can effectively store large volumes of gas and, consequently, have been identified as a potential unconventional energy source. First recognized to exist geologically in the 1960s, significant accumulations of gas hydrate have been found throughout the world. Gas hydrate occurrence is limited to environments such as permafrost regions and subsea sediments because of the pressure and temperature conditions required for their formation and stability. Permafrost-associated gas hydrate accumulations have been discovered in many regions of the Arctic, including Russia, Canada, and the North Slope of Alaska. Gas hydrate research has a long history in northern Alaska. This research includes the drilling, coring, and well log evaluation of two gas hydrate stratigraphic test wells and two resource assessments of gas hydrates on the Alaska North Slope. Building upon these previous investigations, this report provides a summary of the pertinent well log, gas hydrate, and stratigraphic data for key wells related to gas hydrate occurrence in the north-central North Slope. The data are presented in nine well log correlation sections with 122 selected wells to provide a regional context for gas hydrate accumulations and the relation of the accumulations to key stratigraphic horizons and to the base of the ice-bearing permafrost. Also included is a well log database that lists the location, available well logs, depths, and other pertinent information for each of the wells on the correlation section.

  8. [Raman spectroscopic investigation of hydrogen storage in nitrogen gas hydrates].

    PubMed

    Meng, Qing-guo; Liu, Chang-ling; Ye, Yu-guang; Li, Cheng-feng

    2012-08-01

    Recently, hydrogen storage using clathrate hydrate as a medium has become a hotspot of hydrogen storage research In the present paper, the laser Raman spectroscopy was used to study the hydrogen storage in nitrogen hydrate. The synthetic nitrogen hydrate was reacted with hydrogen gas under relatively mild conditions (e.g., 15 MPa, -18 degrees C). The Raman spectra of the reaction products show that the hydrogen molecules have enclathrated the cavities of the nitrogen hydrate, with multiple hydrogen cage occupancies in the clathrate cavities. The reaction time is an important factor affecting the hydrogen storage in nitrogen hydrate. The experimental results suggest that nitrogen hydrates are expected to be an effective media for hydrogen storage.

  9. Gas Hydrate-Sediment Morphologies Revealed by Pressure Core Analysis

    NASA Astrophysics Data System (ADS)

    Holland, M.; Schultheiss, P.; Roberts, J.; Druce, M.

    2006-12-01

    Analysis of HYACINTH pressure cores collected on IODP Expedition 311 and NGHP Expedition 1 showed gas hydrate layers, lenses, and veins contained in fine-grained sediments as well as gas hydrate contained in coarse-grained layers. Pressure cores were recovered from sediments on the Cascadia Margin off the North American West Coast and in the Krishna-Godavari Basin in the Western Bay of Bengal in water depths of 800- 1400 meters. Recovered cores were transferred to laboratory chambers without loss of pressure and nondestructive measurements were made at in situ pressures and controlled temperatures. Gamma density, P-wave velocity, and X-ray images showed evidence of grain-displacing and pore-filling gas hydrate in the cores. Data highlights include X-ray images of fine-grained sediment cores showing wispy subvertical veins of gas hydrate and P-wave velocity excursions corresponding to grain-displacing layers and pore-filling layers of gas hydrate. Most cores were subjected to controlled depressurization experiments, where expelled gas was collected, analyzed for composition, and used to calculate gas hydrate saturation within the core. Selected cores were stored under pressure for postcruise analysis and subsampling.

  10. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    USGS Publications Warehouse

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

  11. GAS HYDRATES AT TWO SITES OF AN ACTIVE CONTINENTAL MARGIN.

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1985-01-01

    Sediment containing gas hydrates from two distant Deep Sea Drilling Project sites (565 and 568), located about 670 km apart on the landward flank of the Middle America Trench, was studied to determine the geochemical conditions that characterize the occurrence of gas hydrates. Site 565 was located in the Pacific Ocean offshore the Nicoya Peninsula of Costa Rica in 3,111 m of water. The depth of the hole at this site was 328 m, and gas hydrates were recovered from 285 and 319 m. Site 568 was located about 670 km to the northwest offshore Guatemala in 2,031 m of water. At this site the hole penetrated to 418 m, and gas hydrates were encountered at 404 m.

  12. Sampling technology for gas hydrates by borehole bottom freezing

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Sun, Youhong; Gao, Ke; Liu, Baochang; Yu, Ping; Ma, Yinlong; Yang, Yang

    2014-05-01

    Exploiting gas hydrate is based on sample drilling, the most direct method to evaluate gas hydrates. At present, the pressure-tight core barrel is a main truth-preserving core sampling tool. This paper puts forward a new gas hydrate-borehole bottom freezing sampling technique. The new sampling technique includes three key components: sampler by borehole bottom freezing, mud cooling system and low temperature mud system. The sampler for gas hydrates by borehole bottom freezing presents a novel approach to the in-situ sampling of gas hydrate. This technique can significantly reduce the sampling pressure and prevent decomposition of the hydrate samples due to the external cold source which may freeze the hydrate cores on the bottom of borehole. The freezing sampler was designed and built based on its thermal-mechanical properties and structure, which has a single action mechanism, control mechanism and freezing mechanism. The technique was tested with a trial of core drilling. Results demonstrate that the new technique can be applied to obtain freezing samples from the borehole bottom. In the sampling process of gas hydrate, mud needs to be kept at a low temperature state to prevent the in-situ decomposition of the hydrate if the temperature of mud is too high. Mud cooling system is an independent system for lowing the temperature of mud that returns to the surface. It can cool mud rapidly, maintain its low temperature steadily, and ensure the temperature of the inlet well mud to meet the gas hydrate drilling operation requirement. The mud cooling system has been applied to the drilling engineering project in the Qilian mountain permafrost in northwest China, and achieved the gas hydrates in permafrost. The ordinary mud could not meet the requirements of good performance at low temperature. Low temperature mud system for NaCl and KCl is developed, whose resistance to the temperature is as low as 20 below zero.In-situ sampling of gas hydrates can be achieved through

  13. Estimates of in situ gas hydrate concentration from resistivity monitoring of gas hydrate bearing sediments during temperature equilibration

    USGS Publications Warehouse

    Riedel, M.; Long, P.E.; Collett, T.S.

    2006-01-01

    As part of Ocean Drilling Program Leg 204 at southern Hydrate Ridge off Oregon we have monitored changes in sediment electrical resistivity during controlled gas hydrate dissociation experiments. Two cores were used, each filled with gas hydrate bearing sediments (predominantly mud/silty mud). One core was from Site 1249 (1249F-9H3), 42.1 m below seafloor (mbsf) and the other from Site 1248 (1248C-4X1), 28.8 mbsf. At Site 1247, a third experiment was conducted on a core without gas hydrate (1247B-2H1, 3.6 mbsf). First, the cores were imaged using an infra-red (IR) camera upon recovery to map the gas hydrate occurrence through dissociation cooling. Over a period of several hours, successive runs on the multi-sensor track (includes sensors for P-wave velocity, resistivity, magnetic susceptibility and gamma-ray density) were carried out complemented by X-ray imaging on core 1249F-9H3. After complete equilibration to room temperature (17-18??C) and complete gas hydrate dissociation, the final measurement of electrical resistivity was used to calculate pore-water resistivity and salinities. The calculated pore-water freshening after dissociation is equivalent to a gas hydrate concentration in situ of 35-70% along core 1249F-9H3 and 20-35% for core 1248C-4X1 assuming seawater salinity of in situ pore fluid. Detailed analysis of the IR scan, X-ray images and split-core photographs showed the hydrate mainly occurred disseminated throughout the core. Additionally, in core 1249F-9H3, a single hydrate filled vein, approximately 10 cm long and dipping at about 65??, was identified. Analyses of the logging-while-drilling (LWD) resistivity data revealed a structural dip of 40-80?? in the interval between 40 and 44 mbsf. We further analyzed all resistivity data measured on the recovered core during Leg 204. Generally poor data quality due to gas cracks allowed analyses to be carried out only at selected intervals at Sites 1244, 1245, 1246, 1247, 1248, 1249, and 1252. With a few

  14. Methane Gas Hydrate Decomposition in a Porous Medium Upon Injection of a Warm Carbon Dioxide Gas

    NASA Astrophysics Data System (ADS)

    Khasanov, M. K.; Shagapov, V. Sh.

    2016-09-01

    The characteristic features of methane gas hydrate decomposition upon injection of a warm carbon dioxide gas into a porous medium saturated with methane and its hydrate are investigated. A mathematical model is presented for heat and mass transfer in a porous medium accompanied by substitution of methane for carbon dioxide gas in the original gas hydrate. Self-similar solutions of a one-dimensional problem that describe the distribution of basic parameters in a stratum have been constructed. It is shown that there are solutions according to which methane gas hydrate may decompose either with the formation of carbon dioxide gas hydrate alone, or with the formation of both carbon dioxide gas hydrate and a mixture of methane with water. Critical diagrams of the existence of each type of solutions have been drawn.

  15. Cryopegs as destabilization factor of intra-permafrost gas hydrates

    NASA Astrophysics Data System (ADS)

    Chuvilin, Evgeny; Bukhanov, Boris; Istomin, Vladimir

    2016-04-01

    A characteristic feature of permafrost soils in the Arctic is widespread intra-permafrost unfrozen brine lenses - cryopegs. They are often found in permafrost horizons in the north part of Western Siberia, in particular, on the Yamal Peninsula. Cryopegs depths in permafrost zone can be tens and hundreds of meters from the top of frozen strata. The chemical composition of natural cryopegs is close to sea waters, but is characterized by high mineralization. They have a sodium-chloride primary composition with a minor amount of sulphate. Mineralization of cryopegs brine is often hundreds of grams per liter, and the temperature is around -6…-8 °C. The formation of cryopegs in permafrost is associated with processes of long-term freezing of sediments and cryogenic concentration of salts and salt solutions in local areas. The cryopegs' formation can take place in the course of permafrost evolution at the sea transgressions and regressions during freezing of saline sea sediments. Very important feature of cryopegs in permafrost is their transformation in the process of changing temperature and pressure conditions. As a result, the salinity and chemical composition are changed and in addition the cryopegs' location can be changed during their migration. The cryopegs migration violates the thermodynamic conditions of existence intra-permafrost gas hydrate formations, especially the relic gas hydrates deposits, which are situated in the shallow permafrost up to 100 meters depth in a metastable state [1]. The interaction cryopegs with gas hydrates accumulations can cause decomposition of intra-permafrost hydrates. Moreover, the increasing of salt and unfrozen water content in sedimentary rocks sharply reduce the efficiency of gas hydrates self-preservation in frozen soils. It is confirmed by experimental investigations of interaction of frozen gas hydrate bearing sediments with salt solutions [2]. So, horizons with elevated pressure can appear, as a result of gas hydrate

  16. Laboratory analysis of gas hydrate cores for evaluation of reservoir conditions. Final report

    SciTech Connect

    Holder, G.D.

    1984-06-01

    Methodology and procedures for the study of hydrate cores are detailed. Topics discussed are the (1) equipment and procedures for the formation and evaluation of hydrate cores in the laboratory, (2) the thermodynamic properties of gas hydrates, (3) the enthalpy of hydrate dissociation, (4) conditions in the earth where hydrates can form, (5) kinetics of hydrate formation and dissociation, and (6) heat transfer to gas hydrates. Empirical correlations for these properties and kinetic behavior are given. 24 references, 39 figures, 10 tables.

  17. Numerical Model of Hydrate Formation and Dissociation With Free Gas Flow for a Global Inventory

    NASA Astrophysics Data System (ADS)

    Scandella, B.; Juanes, R.

    2009-12-01

    Methane hydrates hold great potential as an energy resource but also pose the threat, if they dissociate, of contributing to the greenhouse effect. In order to evaluate the risks and opportunities they present, we have developed a numerical model of hydrate formation and dissociation. This one-dimensional, continuum model is simple enough to be applied globally to estimate the total inventory of hydrate and trapped gas, yet captures multiphase flow effects not accounted for in previous inventory estimates. Preliminary results compare behavior regimes in typical active and passive continental margins, including fracture-dominated gas invasion, slow capillary invasion, and dynamic steady states. These results identify the key parameters that need to be estimated at a global scale in order to model the formation of current hydrate accumulations and their response to production and climate change.

  18. Natural gas hydrates and the mystery of the Bermuda Triangle

    SciTech Connect

    Gruy, H.J.

    1998-03-01

    Natural gas hydrates occur on the ocean floor in such great volumes that they contain twice as much carbon as all known coal, oil and conventional natural gas deposits. Releases of this gas caused by sediment slides and other natural causes have resulted in huge slugs of gas saturated water with density too low to float a ship, and enough localized atmospheric contamination to choke air aspirated aircraft engines. The unexplained disappearances of ships and aircraft along with their crews and passengers in the Bermuda Triangle may be tied to the natural venting of gas hydrates. The paper describes what gas hydrates are, their formation and release, and their possible link to the mystery of the Bermuda Triangle.

  19. Geologic implications of gas hydrates in the offshore of India: results of the National Gas Hydrate Program Expedition 01

    USGS Publications Warehouse

    Collett, Timothy S.; Boswell, Ray; Cochran, J.R.; Kumar, Pushpendra; Lall, Malcolm; Mazumdar, Aninda; Ramana, Mangipudi Venkata; Ramprasad, Tammisetti; Riedel, Michael; Sain, Kalachand; Sathe, Arun Vasant; Vishwanath, Krishna

    2014-01-01

    One of the specific objectives of this expedition was to test gas hydrate formation models and constrain model parameters, especially those that account for the formation of concentrated gas hydrate accumulations. The necessary data for characterizing the occurrence of in situ gas hydrate, such as interstitial water chlorinities, core-derived gas chemistry, physical and sedimentological properties, thermal images of the recovered cores, and downhole measured logging data (LWD and/or conventional wireline log data), were obtained from most of the drill sites established during NGHP-01. Almost all of the drill sites yielded evidence for the occurrence of gas hydrate; however, the inferred in situ concentration of gas hydrate varied substantially from site to site. For the most part, the interpretation of downhole logging data, core thermal images, interstitial water analyses, and pressure core images from the sites drilled during NGHP-01 indicate that the occurrence of concentrated gas hydrate is mostly associated with the presence of fractures in the sediments, and in some limited cases, by coarser grained (mostly sand-rich) sediments.

  20. Noble gas encapsulation: clathrate hydrates and their HF doped analogues.

    PubMed

    Mondal, Sukanta; Chattaraj, Pratim Kumar

    2014-09-07

    The significance of clathrate hydrates lies in their ability to encapsulate a vast range of inert gases. Although the natural abundance of a few noble gases (Kr and Xe) is poor their hydrates are generally abundant. It has already been reported that HF doping enhances the stability of hydrogen hydrates and methane hydrates, which prompted us to perform a model study on helium, neon and argon hydrates with their HF doped analogues. For this purpose 5(12), 5(12)6(8) and their HF doped analogues are taken as the model clathrate hydrates, which are among the building blocks of sI, sII and sH types of clathrate hydrate crystals. We use the dispersion corrected and gradient corrected hybrid density functional theory for the calculation of thermodynamic parameters as well as conceptual density functional theory based reactivity descriptors. The method of the ab initio molecular dynamics (AIMD) simulation is used through atom centered density matrix propagation (ADMP) techniques to envisage the structural behaviour of different noble gas hydrates on a 500 fs timescale. Electron density analysis is carried out to understand the nature of Ng-OH2, Ng-FH and Ng-Ng interactions. The current results noticeably demonstrate that the noble gas (He, Ne, and Ar) encapsulation ability of 5(12), 5(12)6(8) and their HF doped analogues is thermodynamically favourable.

  1. Gas hydrates and possible environmental risks offshore South Chile

    NASA Astrophysics Data System (ADS)

    Vargas Cordero, I.; Tinivella, U.; Accaino, F.; Loreto, M. F.; Fanucci, F.; Reichert, C.

    2009-04-01

    Gas hydrates and free gas presence was detected within marine sediments, offshore South Chile, by using seismic analysis. We analysed dataset located offshore South Chile; in particular, two seismic lines were analysed. The first one is located in the northern sector offshore Arauco (38°S) and the second one located in the southern sector offshore Coyhaique (44°S).We used the pre-stack depth migration method (Kirchhoff algorithm) to obtain an accurate velocity model and the real geometry of the Bottom Simulating Reflector (BSR), representing the base of the gas hydrate layer. The velocity was determined analysing iteratively the Common Image Gathers (CIGs) by using Seismic Unix and home code created ad hoc to convert the non-flatness of the reflections in the CIGs into velocity error. Moreover, we converted the final velocity model in terms of gas hydrate and free gas concentrations by using the modified Biot's theory, in which we compared the final velocity model with a theoretical model in absence of gas. Thus, the positive velocity anomalies were associated to gas hydrate presence, while the negative velocity anomalies were associated to free gas presence. In addition, the geothermal gradient was estimated by BSR and seafloor depths and relative BSR amplitude were calculated to correlate the hydrate/free gas concentration to the BSR characteristic. The velocity model allowed us to detect the hydrate layer above the bottom simulating reflector, and the free gas layer below it. The velocity field is affected by strong lateral variation, showing maximum and minimum values in the southern sector. In the southern sector, the highest gas hydrate and free gas concentrations are detected (23% and 2.4% of total volume respectively), even if the high velocity can be partially caused by overcompaction. Here, the BSR depth varies from 250 meter below seafloor (in the middle of the accretionary prism) to 130 meter below seafloor (in the structural high), reaching its

  2. Evaluation of phase envelope on natural gas, condensate and gas hydrate

    NASA Astrophysics Data System (ADS)

    Promkotra, S.; Kangsadan, T.

    2015-03-01

    The experimentally gas hydrate are generated by condensate and natural gas. Natural gas and condensate samples are collected from a gas processing plant where is situated in the northeastern part of Thailand. Physical properties of the API gravity and density of condensate are presented in the range of 55-60° and 0.71-0.76 g/cm3. The chemical compositions of petroleum-field water are analyzed to evaluate the genesis of gas hydrate by experimental procedure. The hydrochemical compositions of petroleum-field waters are mostly the Na-Cl facies. This condition can estimate how the hydrate forms. Phase envelope of condensate is found only one phase which is liquid phase. The liquid fraction is 100% at 15°C and 101.327 kPa, with the critical pressure and temperature of 2,326 kPa and 611.5 K. However, natural gas can be separated in three phases which are vapor, liquid and solid phase with the pressure and temperature at 100 kPa and 274.2 K. The hydrate curves explicit both hydrate zone and nonhydrate zone. Phase envelope of gas hydrate from the phase diagram indicates the hydrate formation. The experimental results of hydrate form can correlate to the hydrate curve. Besides, the important factor of hydrate formation depends on impurity in the petroleum system.

  3. Gas hydrates in the deep water Ulleung Basin, East Sea, Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae

    2016-04-01

    Studies on gas hydrates in the deep-water Ulleung Basin, East Sea, Korea was initiated by the Korea Institute of Geoscience and Mineral Resources (KIGAM) to secure the future energy resources in 1996. Bottom simulating reflectors (BSRs) were first identified on seismic data collected in the southwestern part of the basin from 1998 to 1999. Regional geophysical surveys and geological studies of gas hydrates in the basin have been carried out by KIGAM from 2000 to 2004. The work included 12,367 km of 2D multi-channel seismic reflection lines and 38 piston cores 5 to 8 m long. As a part of the Korean National Gas Hydrate Program that has been performed since 2005, 6690 km of 2D multi-channel reflection seismic lines, 900 km2 of 3D seismic data, 69 piston cores and three PROD cores were additionally collected. In addition, two gas hydrate drilling expeditions were performed in 2007 and 2010. Cracks generally parallel to beddings caused by the dissociation of gas hydrate were often observed in cores. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data showed clear and wide-spread bottom-simulating reflectors (BSRs). The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone. Several vertical to sub-vertical chimney-like blank zones up to several kilometers in diameter were also identified in the study area. They are often associated with velocity pull-up structures that are interpreted due to higher velocity in gas hydrate-bearing deposits. Seismic velocity analysis also showed a high velocity anomaly within the pull-up structure. Gas hydrate samples were collected from the shallow sedimentary section of blanking zone by piston coring in 2007. BSRs mainly occur in the southern part of the basin. They also locally observed in the

  4. In-situ Micro-structural Studies of Gas Hydrate Formation in Sedimentary Matrices

    NASA Astrophysics Data System (ADS)

    Kuhs, Werner F.; Chaouachi, Marwen; Falenty, Andrzej; Sell, Kathleen; Schwarz, Jens-Oliver; Wolf, Martin; Enzmann, Frieder; Kersten, Michael; Haberthür, David

    2015-04-01

    The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in-situ with sub-micron resolution. Here, we report on synchrotron-based micro-tomographic studies by which the nucleation and growth processes of gas hydrate were observed in different sedimentary matrices (natural quartz, glass beds with different surface properties, with and without admixtures of kaolinite and montmorillonite) at varying water saturation. The nucleation sites can be easily identified and the growth pattern is clearly established. In under-saturated sediments the nucleation starts at the water-gas interface and proceeds from there to form predominantly isometric single crystals of 10-20μm size. Using a newly developed synchrotron-based method we have determined the crystallite size distributions (CSD) of the gas hydrate in the sedimentary matrix confirming in a quantitative and statistically relevant manner the impressions from the tomographic reconstructions. It is noteworthy that the CSDs from synthetic hydrates are distinctly smaller than those of natural gas hydrates [1], which suggest that coarsening processes take place in the sedimentary matrix after the initial hydrate formation. Understanding the processes of formation and coarsening may eventually permit the determination of the age of gas hydrates in sedimentary matrices [2], which are largely unknown at present. Furthermore, the full micro-structural picture and its evolution will enable quantitative digital rock physics modeling to reveal poroelastic properties and in this way to support the exploration and exploitation of gas hydrate resources in the future. [1] Klapp S.A., Hemes S., Klein H., Bohrmann G., McDonald I., Kuhs W.F. Grain size measurements of natural gas hydrates. Marine Geology 2010; 274(1-4):85-94. [2] Klapp S.A., Klein H, Kuhs W.F. First determination of gas hydrate

  5. Gas production from oceanic Class 2 hydrate accumulations

    SciTech Connect

    Moridis, G.J.; Reagan, M.T.

    2007-02-01

    Gas hydrates are solid crystalline compounds in which gasmolecules are lodged within the lattices of ice crystals. The vastamounts of hydrocarbon gases that are trapped in hydrate deposits in thepermafrost and in deep ocean sediments may constitute a promising energysource. Class 2 hydrate deposits are characterized by a Hydrate-BearingLayer (HBL) that is underlain by a saturated zone of mobile water. Inthis study we investigated three methods of gas production via verticalwell designs. A long perforated interval (covering the hydrate layer andextending into the underlying water zone) yields the highest gasproduction rates (up to 20 MMSCFD), but is not recommended for long-termproduction because of severe flow blockage caused by secondary hydrateand ice. A short perforated interval entirely within the water zoneallows long-term production, but only at rates of 4.5 7 MMSCFD. A newwell design involving localized heating appears to be the most promising,alleviating possible blockage by secondary hydrate and/or ice near thewellbore) and delivering sustainably large, long-term rates (10-15MMSCFD).The production strategy involves a cyclical process. During eachcycle, gas production continuously increases, while the correspondingwater production continuously decreases. Each cycle is concluded by acavitation event (marked by a precipitous pressure drop at the well),brought about by the inability of thesystem to satisfy the constant massproduction rate QM imposed at the well. This is caused by the increasinggas contribution to the production stream, and/or flow inhibition causedby secondary hydrate and/or ice. In the latter case, short-term thermalstimulation removes the blockage. The results show that gas productionincreases (and the corresponding water-to-gas ratio RWGC decreases) withan increasing(a) QM, (b) hydrate temperature (which defines its stabilityfor a given pressure), and (c) intrinsic permeability. Lower initialhydrate saturations lead initially to higher gas

  6. Free energy landscape and molecular pathways of gas hydrate nucleation

    NASA Astrophysics Data System (ADS)

    Bi, Yuanfei; Porras, Anna; Li, Tianshu

    2016-12-01

    Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), pB histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the pB histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

  7. Properties of samples containing natural gas hydrate from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well, determined using Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI)

    USGS Publications Warehouse

    Winters, W.J.

    1999-01-01

    As part of an ongoing laboratory study, preliminary acoustic, strength, and hydraulic conductivity results are presented from a suite of tests conducted on four natural-gas-hydrate-containing samples from the Mackenzie Delta JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well. The gas hydrate samples were preserved in pressure vessels during transport from the Northwest Territories to Woods Hole, Massachusetts, where multistep tests were performed using GHASTLI (Gas Hydrate And Sediment Test Laboratory Instrument), which recreates pressure and temperature conditions that are stable for gas hydrate. Properties and changes in sediment behaviour were measured before, during, and after controlled gas hydrate dissociation. Significant amounts of gas hydrate occupied the sample pores and substantially increased acoustic velocity and shear strength.

  8. Tectonic Controls on Gas Hydrate Distribution off SW Taiwan

    NASA Astrophysics Data System (ADS)

    Berndt, C.; Chi, W. C.; Jegen, M. D.; Muff, S.; Hölz, S.; Lebas, E.; Sommer, M.; Lin, S.; Liu, C. S.; Lin, A. T.; Klaucke, I.; Klaeschen, D.; Chen, L.; Kunath, P.; McIntosh, K. D.; Feseker, T.

    2015-12-01

    The northern part of the South China Sea is characterized by wide-spread occurrence of bottom simulating reflectors (BSR), indicating the presence of marine gas hydrates. Because the area covers both the tectonically inactive passive margin and the northern termination of the Manila Trench subduction zone while sediment input is broadly similar, this area provides an excellent opportunity to study the influence of tectonic processes on the dynamics of gas hydrate systems. Long-offset multi-channel seismic data show that movement along thrust faults and blind thrust faults caused anticlinal ridges on the active margin, while faults are absent on the passive margin. This coincides with high-hydrate saturations derived from ocean bottom seismometer data and controlled source electromagnetic data, and conspicuous high-amplitude reflections in P-Cable 3D seismic data above the BSR in the anticlinal ridges of the active margin. On the contrary, all geophysical evidence for the passive margin points to normal- to low-hydrate saturations. Geochemical analysis of gas samples collected at seep sites on the active margin show methane with heavy δ13C isotope composition, while gas collected on the passive margin shows highly depleted (light) carbon isotope composition. Thus, we interpret the passive margin as a typical gas hydrate province fuelled by biogenic production of methane and the active margin gas hydrate system as a system that is fuelled not only by biogenic gas production but also by additional advection of thermogenic methane from the subduction system. The location of the highest gas hydrate saturations in the hanging wall next to the thrust faults suggests that the thrust faults represent pathways for the migration of methane. Our findings suggest that the most promising gas hydrate occurrences for exploitation of gas hydrate as an energy source may be found in the core of the active margin roll over anticlines immediately above the BSR and that high

  9. Hydration of Gas-Phase Ions Formed by Electrospray Ionization

    PubMed Central

    Rodriguez-Cruz, Sandra E.; Klassen, John S.; Williams, Evan R.

    2005-01-01

    The hydration of gas-phase ions produced by electrospray ionization was investigated. Evidence that the hydrated ions are formed by two mechanisms is presented. First, solvent condensation during the expansion inside the electrospray source clearly occurs. Second, some solvent evaporation from more extensively solvated ions or droplets is apparent. To the extent that these highly solvated ions have solution-phase structures, then the final isolated gas-phase structure of the ion will be determined by the solvent evaporation process. This process was investigated for hydrated gramicidin S in a Fourier-transform mass spectrometer. Unimolecular dissociation rate constants of isolated gramicidin S ions with between 2 and 14 associated water molecules were measured. These rate constants increased from 16 to 230 s−1 with increasing hydration, with smaller values corresponding to magic numbers. PMID:10497808

  10. Modeling heating curve for gas hydrate dissociation in porous media.

    PubMed

    Dicharry, Christophe; Gayet, Pascal; Marion, Gérard; Graciaa, Alain; Nesterov, Anatoliy N

    2005-09-15

    A method for modeling the heating curve for gas hydrate dissociation in porous media at isochoric conditions (constant cell volume) is presented. This method consists of using an equation of state of the gas, the cumulative volume distribution (CVD) of the porous medium, and a van der Waals-Platteeuw-type thermodynamic model that includes a capillary term. The proposed method was tested to predict the heating curves for methane hydrate dissociation in a mesoporous silica glass for saturated conditions (liquid volume = pore volume) and for a fractional conversion of water to hydrate of 1 (100% of the available water was converted to hydrate). The shape factor (F) of the hydrate-water interface was found equal to 1, supporting a cylindrical shape for the hydrate particles during hydrate dissociation. Using F = 1, it has been possible to predict the heating curve for different ranges of pressure and temperature. The excellent agreement between the calculated and experimental heating curves supports the validity of our approach.

  11. Rock magnetism of gas hydrate-bearing rocks in the Nankai Trough, offshore SW Japan

    NASA Astrophysics Data System (ADS)

    Kars, M. A.; Kodama, K.

    2013-12-01

    For the last decade, focus on gas hydrates has been increasing because of their potential value as an energy resource and their possible impact on climate change. Convergent margins, such as the Cascadia Margin (offshore Oregon, USA) and the Nankai Trough (offshore SW Japan) are favorable locations for the formation of gas hydrates. High amplitude bottom simulating reflectors (BSR) are often considered to be indicators of the presence of gas hydrates. Rock magnetism has also appeared to be a suitable approach. Here we focus on gas hydrate-bearing rocks from hole C0008C drilled in 2008 during the IODP Expedition 316, part of the Nankai Trough Seismogenic Experiment Zone (NanTroSEIZE) drilling project. Site C0008 is located at the slope basin seaward of the splay fault. In hole C0008C, seven gas hydrates occurrences were identified by local Cl minima from ~70 to ~170 m CSF (core depth below seafloor). We conducted a high-resolution rock magnetic study from ~70 to ~110 m CSF in order to determine the nature, size and concentration of the magnetic minerals present in the cores. As a preliminary study, about 200 discrete samples were analyzed. In addition, comparison with geochemical data and scanning electron microscope observations were made.

  12. Detection of gas hydrate with downhole logs and assessment of gas hydrate concentrations (saturations) and gas volumes on the Blake Ridge with electrical resistivity log data

    USGS Publications Warehouse

    Collett, T.S.; Ladd, J.

    2000-01-01

    Let 164 of the Ocean Drilling Program was designed to investigate the occurrence of gas hydrate in the sedimentary section beneath the Blake Ridge on the southeastern continental margin of North America. Site 994, and 997 were drilled on the Blake Ridge to refine our understanding of the in situ characteristics of natural gas hydrate. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas hydrate-bearing sediments. Downhole logging tool strings deployed on Leg 164 included the Schlumberger quad-combination tool (NGT, LSS/SDT, DIT, CNT-G, HLDT), the Formation MicroScanner (FMS), and the Geochemical Combination Tool (GST). Electrical resistivity (DIT) and acoustic transit-time (LSS/SDT) downhole logs from Sites 994, 995, and 997 indicate the presence of gas hydrate in the depth interval between 185 and 450 mbsf on the Blake Ridge. Electrical resistivity log calculations suggest that the gas hydrate-bearing sedimentary section on the Blake Ridge may contain between 2 and 11 percent bulk volume (vol%) gas hydrate. We have determined that the log-inferred gas hydrates and underlying free-gas accumulations on the Blake Ridge may contain as much as 57 trillion m3 of gas.

  13. Gas hydrate dissociation in sediments: Pressure-temperature evolution

    NASA Astrophysics Data System (ADS)

    Kwon, Tae-Hyuk; Cho, Gye-Chun; Santamarina, J. Carlos

    2008-03-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. A comprehensive formulation is derived for the prediction of fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation considers pressure- and temperature-dependent volume changes in all phases, effective stress-controlled sediment compressibility, capillarity, and the relative solubilities of fluids. Salient implications are explored through parametric studies. The model properly reproduces experimental data, including the PT evolution along the phase boundary during dissociation and the effect of capillarity. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. When the sediment stiffness is high, the generated pore pressure reflects thermal and pressure changes in water, hydrate, and mineral densities. Comparative analyses for CO2 and CH4 highlight the role of gas solubility in excess pore fluid pressure generation. Dissociation in small pores experiences melting point depression due to changes in water activity, and lower pore fluid pressure generation due to the higher gas pressure in small gas bubbles. Capillarity effects may be disregarded in silts and sands, when hydrates are present in nodules and lenses and when the sediment experiences hydraulic fracture.

  14. Gas migration in the Terrebonne Basin gas hydrate system, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Cook, A.; Hillman, J. I. T.; Sawyer, D.

    2015-12-01

    The Terrebonne Basin is a salt bounded mini-basin in the northeast section of the Walker Ridge protraction area in the Gulf of Mexico (water depth ~2 km), where the Gas Hydrate Joint Industry Project Leg 2 identified gas hydrate via logging-while-drilling in 2009. The Terrebonne Basin is infilled by gently dipping mud-rich sedimentary sequences with several sand units. Gas hydrate was detected in two significant reservoir sands 10s of meters in thickness, a number of thin 1 to 3 meter-thick sands, and in thick, 10-100 meter intervals of marine muds with gas hydrate in near-vertical fractures. In this research, we combine 3D seismic mapping with wavelet and travel time analysis to interpret gas migration mechanisms in each hydrate-bearing sand. Our analyses suggest that the Orange sand, a main reservoir unit, is sourced from below the gas hydrate stability zone and, the 2.5 meter-thick Red sand (also called 'Unit A'), is sourced locally. Our primary evidence is from seismic amplitudes across the two sands that show distinctly different patterns. The Orange sand has distinct high amplitudes within the gas hydrate stability zone and negative amplitudes suggesting free gas below the gas hydrate stability zone. The Red sand, in contrast, has no free gas source below the stability zone and the hydrate distribution as described by high amplitudes suggests that hydrate distribution is spotty. This may imply that gas generation is occurring sporadically in the surrounding marine mud units; this matches with a model of the Red sand that suggests it is sourced locally. These preliminary observations require further refinement but they indicate that fundamentally different migration mechanisms are occurring within a single hydrate system.

  15. The particle size effect on Gas Hydrate Formation in powdered silica particles

    NASA Astrophysics Data System (ADS)

    Kawasaki, T.; Lu, H.; Ripmeester, J. A.; Zeng, H.; Fujii, T.; Nakamizu, M.

    2007-12-01

    Based on the investigations in the past years, it has been recognized that methane hydrates in Nankai Trough primarily occur in turbidite sediments (Fujii et al. 2005; Uchida et al., 2005). Turbidite is composed of a set of sediments, generally becoming finer upward in particle size, from coarse sand to clay (Bouma, 1962). In natural environment the formation of methane hydrate will be inevitably subject to the influence of sediments, so the modes of gas hydrate formation and occurrence might be different in the sediments with various particle sizes and mineral compositions. The elucidation of this issue, how sediments affect methane hydrate formation and occurrence will help in efficient hydrate exploration, accurate estimation of hydrate reserve, and the design of hydrate production method. In this research, we especially studied the particle size effect on the water conversion degree to hydrate using a set of powdered silica particles with the size from medium silt (<20 μm) to medium sand (250 ~ 500 μm). The test specimens were saturated with 3.5% NaCl solution, simulating the interstitial water of marine sediments, and reacted with methane gas at the pressure of ~ 10 MPa and temperature of 3° C. The water conversion degree to hydrate in a test specimen was estimated with the amount of gas that was clathrated in hydrate. The obtained results indicate a clear relationship between water conversion degree to hydrate and particle size: only 3.2 % when particle size is <20 μm, increasing dramatically from 5.7% to 82.8 % when particle size changes from ~30 μm (coarse silt) to ~200 μm (fine sand), and almost stable at ~ 80% when particle size is > 250 μm (medium sand). Because the test materials are all silica, the difference in water conversion degree to hydrate should be resulted from physical properties of silica particle, specific surface area, and/or the property confined by silica particle, pore size. This study was carried out as a part of Research

  16. Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample.

    PubMed

    Muraoka, Michihiro; Susuki, Naoko; Yamaguchi, Hiroko; Tsuji, Tomoya; Yamamoto, Yoshitaka

    2016-03-21

    Methane hydrates (MHs) are present in large amounts in the ocean floor and permafrost regions. Methane and hydrogen hydrates are being studied as future energy resources and energy storage media. To develop a method for gas production from natural MH-bearing sediments and hydrate-based technologies, it is imperative to understand the thermal properties of gas hydrates. The thermal properties' measurements of samples comprising sand, water, methane, and MH are difficult because the melting heat of MH may affect the measurements. To solve this problem, we performed thermal properties' measurements at supercooled conditions during MH formation. The measurement protocol, calculation method of the saturation change, and tips for thermal constants' analysis of the sample using transient plane source techniques are described here. The effect of the formation heat of MH on measurement is very small because the gas hydrate formation rate is very slow. This measurement method can be applied to the thermal properties of the gas hydrate-water-guest gas system, which contains hydrogen, CO2, and ozone hydrates, because the characteristic low formation rate of gas hydrate is not unique to MH. The key point of this method is the low rate of phase transition of the target material. Hence, this method may be applied to other materials having low phase-transition rates.

  17. Broadband Seismic Studies at the Mallik Gas Hydrate Research Well

    NASA Astrophysics Data System (ADS)

    Sun, L. F.; Huang, J.; Lyons-Thomas, P.; Qian, W.; Milkereit, B.; Schmitt, D. R.

    2005-12-01

    The JAPEX/JNOC/GSC et al. Mallik 3L-38, 4L-38 and 5L-38 scientific wells were drilled in the MacKenzie Delta, NWT, Canada in early 2002 primarily for carrying out initial tests of the feasibility of producing methane gas from the large gas hydrate deposits there [1]. As part of this study, high resolution seismic profiles, a pseudo-3D single fold seismic volume and broadband (8~180Hz) multi-offset vertical seismic profiles (VSP) were acquired at the Mallik site. Here, we provide details on the acquisition program, present the results of the 2D field profile, and discuss the potential implications of these observations for the structure of the permafrost and gas hydrate zones. These zones have long been problematic in seismic imaging due to the lateral heterogeneities. Conventional seismic data processing usually assume a stratified, weak-contrast elastic earth model. However, in permafrost and gas hydrate zones this approximation often becomes invalid. This leads to seismic wave scattering caused by multi-scale perturbation of elastic properties. A 3D viscoelastic finite difference modeling algorithm was employed to simulate wave propagation in a medium with strong contrast. Parameters in this modeling analysis are based on the borehole geophysical log data. In addition, an uncorrelated Vibroseis VSP data set was studied to investigate frequency-dependent absorption and velocity dispersion. Our results indicate that scattering and velocity dispersion are important for a better understanding of attenuation mechanisms in heterogeneous permafrost and gas hydrate zones. [1] Dallimore, S.R., Collett, T.S., Uchida, T., and Weber, M., 2005, Overview of the science program for the Mallik 2002 Gas Hydrate Production Research Well Program; in Scientific Results from Mallik 2002 Gas Hydrate production Research Well Program, MacKenzie Delta, Northwest Territories, Canada, (ed.) S.R. Dallimore and T.S. Collett; Geological Survey of Canada, Bulletin 585, in press.

  18. Measurements of Gas-Water Relative Permeability for Methane-Hydrate-Bearing Sediments using X-ray Computed-Tomography

    NASA Astrophysics Data System (ADS)

    Konno, Y.; Jin, Y.; Nagao, J.

    2012-04-01

    Oceanic gas hydrate deposits at high saturations have been found within sandy sediments in areas such as the Eastern Nankai Trough and the Gulf of Mexico. The recent discovery of these deposits has stimulated research and development programs exploring the use of gas hydrates as energy resources. Depressurization is thought to be a promising method for gas recovery from gas hydrates deposits; however, considerable water production is expected when this method is applied for oceanic gas hydrate deposits. The prediction of water production is a critical problem for successful gas production from these deposits. The gas-water relative permeability of gas-hydrate-bearing sediments is a key parameter to predict gas-water-ratio (GWR) during gas production. However, the experimental measurement of gas-water relative permeability for gas-hydrate-bearing sediments is a challenging problem due to a phase change (gas hydrate formation/dissociation) during gas-water flooding test. We used X-ray computed tomography (CT) and a newly-developed core holder to measure gas-water relative permeability for gas-hydrate-bearing sediments. X-ray CT was used to image a displacement front and quantify density changes during water flooding test in methane-hydrate-bearing cores. We obtained CT images every two minutes during a water flooding test for a gas-saturated methane-hydrate-bearing core. The movement of displacement front was captured from these CT images. Quantitative analysis of density change was also done to analyze the change of gas/water saturations. We developed a multi-sensor-tap core holder to minimize capillary end effect on the pressure measurements. To be able to obtain CT images by X-ray, the core holder was made of aluminum alloy. We successfully measured pressure differences of the intermediate section of the core during water flooding test. The change of pressure differences during water flooding test showed strong correlation with the movement of displacement front

  19. Gas hydrate quantification through effective medium theories-A comparison

    NASA Astrophysics Data System (ADS)

    Chand, S.; Minshull, T. A.; Gei, D.; Carcione, J. M.

    2003-04-01

    The presence of gas hydrate in oceanic sediments is normally identified by a Bottom Simulating Reflector (BSR), the reflection event with reversed polarity subparallel to the seafloor. The presence or absence of BSR and its relative amplitude were mainly used in studies for quantifying the amount of gas hydrate present in the oceanic sediments. Recent studies have shown that the BSR is not a necessary criterion for the presence of gas hydrates; rather its presence depends on the type of sediments and in situ conditions. Also the presence of a BSR does not guarantee hydrate in sediment pore space above the gas hydrate stability zone (GHSZ). It is found that the presence of gas hydrate in oceanic sediments alters the acoustic properties of the composite medium. In this context several theories have been developed to predict the properties of sediments, and thereby quantifying the amount of gas hydrate present as the deviation from the predicted parameters of the sediments without gas hydrate. We compared four major theories. The first theory follows a method of weighted averaging of different equations to fit the observed data. The second method uses an initial model at critical porosity, and predicts the properties at other porosities using theories of composite medium at higher and lower porosities, and laws governing fluid flow. The third theory follows a similar approach but uses a different method to approximate the effect of fluid flow and attenuation. The fourth method uses the theory of self-consistent approximation (SCA) and differential effective medium (DEM) defining the connectivity and coexistence of different phases. In this study we have made a comparison of all these theories using standard values for physical constants, for various ranges of variables including clay content, hydrate saturation and porosity. The comparison shows that the prediction will be only consistent if we include V_p and V_s for prediction, as V_s predicted by each model is

  20. Degrading permafrost and gas hydrate under the Beaufort Shelf and marine gas hydrate on the adjacent continental slope

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Dallimore, S. R.; Hughes Clarke, J. E.; Blasco, S.; Melling, H.; Lundsten, E.; Vagle, S.; Collett, T. S.

    2011-12-01

    The sub-seafloor under the Arctic Shelf is arguably the part of the Earth that is undergoing the most dramatic warming. In the southern Beaufort Sea, the shelf area was terrestrially exposed during much of the Quaternary period when sea level was ~120m lower than present. As a consequence, many areas are underlain by >600m of ice-bonded permafrost that conditions the geothermal regime such that the base of the methane hydrate stability can be >1000m deep. Marine transgression has imposed a change in mean annual surface temperature from -15°C or lower during periods of terrestrial exposure, to mean annual sea bottom temperatures near 0°C. The thermal disturbance caused by transgression is still influencing the upper km of subsurface sediments. Decomposition of gas hydrate is inferred to be occurring at the base and the top of the gas hydrate stability zone. As gas hydrate and permafrost intervals degrade, a range of processes occur that are somewhat unique to this setting. Decomposition of gas hydrate at depth can cause sediment weakening, generate excess pore water pressure, and form free gas. Similarly, thawing permafrost can cause thaw consolidation, liberate trapped gas bubbles in ice bonded permafrost. Understanding the connection between deep subsurface processes generated by transgression, surficial sediment processes near the seafloor, and gas flux into the ocean and atmosphere is important to assessing geohazard and environmental conditions in this setting. In contrast, conditions for marine gas hydrate formation occur on the adjacent continental slope below ~270m water depths. In this paper, we present field observations of gas venting from three geologically distinct environments in the Canadian Beaufort Sea, two on the shelf and one on the slope. A complimentary paper by Dallimore et al reviews the geothermal changes conditioning this environment. Vigorous methane venting is occurring over Pingo-Like-Features (PLF) on the mid-shelf. Diffuse venting of

  1. Method and apparatus for recovering a gas from a gas hydrate located on the ocean floor

    DOEpatents

    Wyatt, Douglas E.

    2001-01-01

    A method and apparatus for recovering a gas from a gas hydrate on the ocean floor includes a flexible cover, a plurality of steerable base members secured to the cover, and a steerable mining module. A suitable source for inflating the cover over the gas hydrate deposit is provided. The mining module, positioned on the gas hydrate deposit, is preferably connected to the cover by a control cable. A gas retrieval conduit or hose extends upwardly from the cover to be connected to a support ship on the ocean surface.

  2. Gas hydrates over the Egyptian Med. Coastal waters

    NASA Astrophysics Data System (ADS)

    Sharaf El Din, Sayed; Nassar, Marawan

    2010-05-01

    Natural gas hydrates occur worldwide in different oceanic environments, especially in areas of onshore and offshore permafrost and in sediments on continental slops, PT conditions required to initiate the hydrate formation and to stabilize its structure are encountered along the continental slop of the nile delta. Hydocarbon gases in the Nile Delta are not geochemically homogeneous, originating from the decomposition of organic matter by biochemical and thermal processes. The structure of the hydrate determines the type of gas molecules contained. Although Gas hydrates exist over the Egyptian Med. Coastal waters, very little is known on its, origin, quality and quantity. Several studies had been done by several oil companies in the vicinity of the Egyptian territory. High concentration in thin, patchy zones just above the BSR may be, destabilized by Tectonic uplift or climate changes. The seismic profiles taken over the continental slope of the Nile Delta from Damietta to Rashid gave strong evidence of MH with very clear BSR. Geological and geochemical setting of Gas Hydrate Reservoir in front of the Egyptian Nile Delta need more investigations.

  3. Gas hydrate accumulation at the Hakon Mosby Mud Volcano

    USGS Publications Warehouse

    Ginsburg, G.D.; Milkov, A.V.; Soloviev, V.A.; Egorov, A.V.; Cherkashev, G.A.; Vogt, P.R.; Crane, K.; Lorenson, T.D.; Khutorskoy, M.D.

    1999-01-01

    Gas hydrate (GH) accumulation is characterized and modeled for the Hakon Mosby mud volcano, ca. 1.5 km across, located on the Norway-Barents-Svalbard margin. Pore water chemical and isotopic results based on shallow sediment cores as well as geothermal and geomorphological data suggest that the GH accumulation is of a concentric pattern controlled by and formed essentially from the ascending mud volcano fluid. The gas hydrate content of sediment peaks at 25% by volume, averaging about 1.2% throughout the accumulation. The amount of hydrate methane is estimated at ca. 108 m3 STP, which could account for about 1-10% of the gas that has escaped from the volcano since its origin.

  4. Gas Hydrate Research Coring and Downhole Logging Operational Protocol

    NASA Astrophysics Data System (ADS)

    Collett, T. S.; Riedel, M.; Malone, M.

    2006-12-01

    Recent gas hydrate deep coring and downhole logging projects, including ODP Leg 204, IODP Expedition 311, and the India NGHP-01 effort have contributed greatly to our understanding of the geologic controls on the occurrence of gas hydrate. These projects have also built on the relatively sparse history of gas hydrate drilling experience to collectively develop a unique operational protocol to examine and sample gas hydrate in nature. The ideal gas hydrate research drill site in recent history, consists of at least three drill holes, with the first hole dedicated to LWD/MWD downhole logging in order to identify intervals to be pressurized cored and to collect critical petrophysical data. The second hole is usually dedicated for continuous coring operations. The third hole is used for special downhole tool measurements such as pressure coring and wire line logging. There is a strong scientific need to obtain LWD/MWD data prior to coring. The coring operations are complemented by frequent deployment of the PCS/HYACINTH pressure core systems. It is essential to know what the gas hydrate concentrations and vertical distribution are before deploying the available pressure core systems in order to choose the optimum depths for pressure coring operations. The coring operations are also complemented by frequent sampling for interstitial water, headspace gas, and microbiological analyses. Although those samples will be taken at relatively regular depths, the sampling frequency can be adjusted if gas hydrate concentrations and distribution can be forward predicted through the analysis of the LWD/MWD pre-core logging surveys. After completing the LWD/MWD logging program, usually as a dedicated drilling leg, field efforts will switch to conventional and pressure-controlled coring operations at each of the sites drilled during the LWD/MWD campaign. The standard continuous core hole will usually include APC coring to an expected refusal depth of ~100 mbsf; each hole is usually

  5. Scientific results of the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2)

    USGS Publications Warehouse

    Ryu, Byong-Jae; Collett, Timothy S.; Riedel, Michael; Kim, Gil-Young; Chun, Jong-Hwa; Bahk, Jang-Jun; Lee, Joo Yong; Kim, Ji-Hoon; Yoo, Dong-Geun

    2013-01-01

    As a part of Korean National Gas Hydrate Program, the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) was conducted from 9 July to 30 September, 2010 in the Ulleung Basin, East Sea, offshore Korea using the D/V Fugro Synergy. The UBGH2 was performed to understand the distribution of gas hydrates as required for a resource assessment and to find potential candidate sites suitable for a future offshore production test, especially targeting gas hydrate-bearing sand bodies in the basin. The UBGH2 sites were distributed across most of the basin and were selected to target mainly sand-rich turbidite deposits. The 84-day long expedition consisted of two phases. The first phase included logging-while-drilling/measurements-while-drilling (LWD/MWD) operations at 13 sites. During the second phase, sediment cores were collected from 18 holes at 10 of the 13 LWD/MWD sites. Wireline logging (WL) and vertical seismic profile (VSP) data were also acquired after coring operations at two of these 10 sites. In addition, seafloor visual observation, methane sensing, as well as push-coring and sampling using a Remotely Operated Vehicle (ROV) were conducted during both phases of the expedition. Recovered gas hydrates occurred either as pore-filling medium associated with discrete turbidite sand layers, or as fracture-filling veins and nodules in muddy sediments. Gas analyses indicated that the methane within the sampled gas hydrates is primarily of biogenic origin. This paper provides a summary of the operational and scientific results of the UBGH2 expedition as described in 24 papers that make up this special issue of the Journal of Marine and Petroleum Geology.

  6. Investigation of shallow gas hydrate occurrence and gas seep activity on the Sakhalin continental slope, Russia

    NASA Astrophysics Data System (ADS)

    Jin, Young Keun; Baranov, Boris; Obzhirov, Anatoly; Salomatin, Alexander; Derkachev, Alexander; Hachikubo, Akihiro; Minami, Hrotsugu; Kuk Hong, Jong

    2016-04-01

    The Sakhalin continental slope has been a well-known gas hydrate area since the first finding of gas hydrate in 1980's. This area belongs to the southernmost glacial sea in the northern hemisphere where most of the area sea is covered by sea ice the winter season. Very high organic carbon content in the sediment, cold sea environment, and active tectonic regime in the Sakhalin slope provide a very favorable condition for occurring shallow gas hydrate accumulation and gas emission phenomena. Research expeditions under the framework of a Korean-Russian-Japanese long-term international collaboration projects (CHAOS, SSGH-I, SSGH-II projects) have been conducted to investigate gas hydrate occurrence and gas seepage activities on the Sakhalin continental slope, Russia from 2003 to 2015. During the expeditions, near-surface gas hydrate samples at more than 30 sites have been retrieved and hundreds of active gas seepage structures on the seafloor were newly registered by multidisciplinary surveys. The gas hydrates occurrence at the various water depths from about 300 m to 1000 m in the study area were accompanied by active gas seepage-related phenomena in the sub-bottom, on the seafloor, and in the water column: well-defined upward gas migration structures (gas chimney) imaged by high-resolution seismic, hydroacoustic anomalies of gas emissions (gas flares) detected by echosounders, seafloor high backscatter intensities (seepage structures) imaged by side-scan sonar and bathymetric structures (pockmarks and mounds) mapped by single/multi-beam surveys, and very shallow SMTZ (sulphate-methane transition zone) depths, strong microbial activities and high methane concentrations measured in sediment/seawater samples. The highlights of the expeditions are shallow gas hydrate occurrences around 300 m in the water depth which is nearly closed to the upper boundary of gas hydrate stability zone in the area and a 2,000 m-high gas flare emitted from the deep seafloor.

  7. Methane storage in dry water gas hydrates.

    PubMed

    Wang, Weixing; Bray, Christopher L; Adams, Dave J; Cooper, Andrew I

    2008-09-03

    Dry water stores 175 v(STP)/v methane at 2.7 MPa and 273.2 K in a hydrate form which is close to the Department of Energy volumetric target for methane storage. Dry water is a silica-stabilized free-flowing powder (95% wt water), and fast methane uptakes were observed (90% saturation uptake in 160 min with no mixing) as a result of the relatively large surface-to-volume ratio of this material.

  8. Gas Phase Hydration of Methyl Glyoxal to Form the Gemdiol

    NASA Astrophysics Data System (ADS)

    Kroll, Jay A.; Axson, Jessica L.; Vaida, Veronica

    2016-06-01

    Methylglyoxal is a known oxidation product of volatile organic compounds (VOCs) in Earth's atmosphere. While the gas phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosol (SOA) continues to be controversial. The gas phase hydration of methylglyoxal to form a gemdiol has not been widely considered for water-restricted environments such as the atmosphere. However, this process may have important consequences for the atmospheric processing of VOCs. We will report on spectroscopic work done in the Vaida laboratory studying the hydration of methylglyoxal and discuss the implications for understanding the atmospheric processing and fate of methylglyoxal and similar molecules.

  9. Formation of natural gas hydrates in marine sediments. Gas hydrate growth and stability conditioned by host sediment properties

    USGS Publications Warehouse

    Clennell, M.B.; Henry, P.; Hovland, M.; Booth, J.S.; Winters, W.J.; Thomas, M.

    2000-01-01

    The stability conditions of submarine gas hydrates (methane clathrates) are largely dictated by pressure, temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of the host sediments also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our model presumes that gas hydrate behaves in a way analogous to ice in the pores of a freezing soil, where capillary forces influence the energy balance. Hydrate growth is inhibited within fine-grained sediments because of the excess internal phase pressure of small crystals with high surface curvature that coexist with liquid water in small pores. Therefore, the base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature, and so nearer to the seabed than would be calculated from bulk thermodynamic equilibrium. The growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, sheets, and lenses in muds; cements in sand and ash layers) can be explained by a requirement to minimize the excess of mechanical and surface energy in the system.

  10. Gas Hydrate Research Database and Web Dissemination Channel

    SciTech Connect

    Micheal Frenkel; Kenneth Kroenlein; V Diky; R.D. Chirico; A. Kazakow; C.D. Muzny; M. Frenkel

    2009-09-30

    To facilitate advances in application of technologies pertaining to gas hydrates, a United States database containing experimentally-derived information about those materials was developed. The Clathrate Hydrate Physical Property Database (NIST Standard Reference Database {number_sign} 156) was developed by the TRC Group at NIST in Boulder, Colorado paralleling a highly-successful database of thermodynamic properties of molecular pure compounds and their mixtures and in association with an international effort on the part of CODATA to aid in international data sharing. Development and population of this database relied on the development of three components of information-processing infrastructure: (1) guided data capture (GDC) software designed to convert data and metadata into a well-organized, electronic format, (2) a relational data storage facility to accommodate all types of numerical and metadata within the scope of the project, and (3) a gas hydrate markup language (GHML) developed to standardize data communications between 'data producers' and 'data users'. Having developed the appropriate data storage and communication technologies, a web-based interface for both the new Clathrate Hydrate Physical Property Database, as well as Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program was developed and deployed at http://gashydrates.nist.gov.

  11. A review and assessment of gas hydrate potential in Çınarcık Basin, Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Sile, Hande; Akin, Cansu; Ucarkus, Gulsen; Namik Cagatay, M.

    2016-04-01

    The Sea of Marmara (NW Turkey), an intracontinental sea between the Mediterranean and Black Seas, is located in a tectonically active region with the formation of shallow gas hydrates and free gas. It is widely known that, Sea of Marmara sediments are organic-rich and conducive to production of methane, which is released on the sea floor through active fault segments of the North Anatolian Fault (Geli et al., 2008). Here we study the gas hydrate potential of the Çınarcık Basin using published data and our core analyses together with gas hydrate stability relations. The gas sampled in the Çınarcık Basin is composed mainly of biogenic methane and trace amounts of heavier hydrocarbons (Bourry et al., 2009). The seafloor at 1273 m depth on the Çınarcık Basin with temperature of 14.5oC and hydrostatic pressure of 127.3 atm corresponds to the physical limit for gas hydrate formation with respect to phase behavior of gas hydrates in marine sediments (Ménot and Bard, 2010). In order to calculate the base of the gas hydrate stability zone in Çınarcık Basin, we plotted T (oC) calculated considering the geothermal gradient versus P (atm) on the phase boundary diagram. Below the seafloor, in addition to hydrostatic pressure (10 Mpa/km), we calculated lithostatic pressure due to sediment thickness considering the MSCL gamma ray density values (~1.7 gr/cm3). Our estimations show that, gas hydrate could be stable in the upper ~20 m of sedimentary succession in Çınarcık Basin. The amount of gas hydrate in the Çınarcık Basin can be determined using the basinal area below 1220 m depth (483 km2) and average thickness of the gas hydrate stability zone (20 m) and the sediment gas hydrate saturation (1.2 % used as Milkov, 2004 suggested). The calculations indicate the potential volume of gas hydrate in Çınarcık Basin as ~11.6x107 m3. Such estimates are helpful for the consideration of gas hydrates as a new energy resource, for assessment of geohazards or their

  12. Site Selection for DOE/JIP Gas Hydrate Drilling in the Northern Gulf of Mexico

    SciTech Connect

    Collett, T.S.; Riedel, M.; Cochran, J.R.; Boswell, R.M.; Kumar, Pushpendra; Sathe, A.V.

    2008-07-01

    Studies of geologic and geophysical data from the offshore of India have revealed two geologically distinct areas with inferred gas hydrate occurrences: the passive continental margins of the Indian Peninsula and along the Andaman convergent margin. The Indian National Gas Hydrate Program (NGHP) Expedition 01 was designed to study the occurrence of gas hydrate off the Indian Peninsula and along the Andaman convergent margin with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. NGHP Expedition 01 established the presence of gas hydrates in Krishna- Godavari, Mahanadi and Andaman basins. The expedition discovered one of the richest gas hydrate accumulations yet documented (Site 10 in the Krishna-Godavari Basin), documented the thickest and deepest gas hydrate stability zone yet known (Site 17 in Andaman Sea), and established the existence of a fully-developed gas hydrate system in the Mahanadi Basin (Site 19).

  13. Holocene Earthquakes, Slope Failures, and Submarine Gas Hydrates at Hydrate Ridge, Cascadia Margin

    NASA Astrophysics Data System (ADS)

    Johnson, J. E.; Goldfinger, C.; Nelson, C. H.

    2002-12-01

    Hydrate Ridge Basin West (HRB-W) is an isolated slope basin located down slope of the well-studied gas hydrate-bearing Hydrate Ridge anticline on the lower slope of the Oregon accretionary wedge. Swath bathymetry and high-resolution sidescan sonar imagery indicate the western flank of Hydrate Ridge is dissected by a large submarine canyon, which serves as the major pathway for sediment transport into the basin. Two piston and companion trigger cores and one 10 ft super kasten core were recently collected from the basin to obtain the Holocene record of slope failure sedimentation events (turbidites/debris flows). To determine the frequency of these slope failures, their temporal effect on seafloor gas hydrate destabilization on Hydrate Ridge, and differentiate between possible triggers responsible for their failure, we compare this slope basin record to the margin-wide earthquake triggered submarine canyon turbidite record preserved in 52 piston and box cores collected in 1999. AMS radiocarbon dating of the submarine canyon turbidites and their margin-wide correlation indicate 13 events have been simultaneously triggered from the Washington to Northern California margins since the eruption of Mt. Mazama 7627 +/-150 cal yr B.P (Zdanowicz et al., 1999) and 18 (5 pre-Mazama -13 post-Mazama) have been simultaneously triggered during the last 10,000 years. We believe the most likely trigger for these events is recurrent subduction zone earthquakes. Initial examination of the new HRB-W cores suggests a possible correlation with the margin-wide turbidite record, with ~20 events occurring above a foraminiferan dominant to radiolarian dominant datum, which can be used as a proxy for the onset of Holocene sedimentation. Planned AMS radiocarbon dating of all events in the new cores will provide more precise ages and test for synchroneity with the margin-wide record. We postulate that earthquake-triggered slope failures are a dominant mechanism that could have a short

  14. Preliminary report on the commercial viability of gas production from natural gas hydrates

    USGS Publications Warehouse

    Walsh, M.R.; Hancock, S.H.; Wilson, S.J.; Patil, S.L.; Moridis, G.J.; Boswell, R.; Collett, T.S.; Koh, C.A.; Sloan, E.D.

    2009-01-01

    Economic studies on simulated gas hydrate reservoirs have been compiled to estimate the price of natural gas that may lead to economically viable production from the most promising gas hydrate accumulations. As a first estimate, $CDN2005 12/Mscf is the lowest gas price that would allow economically viable production from gas hydrates in the absence of associated free gas, while an underlying gas deposit will reduce the viability price estimate to $CDN2005 7.50/Mscf. Results from a recent analysis of the simulated production of natural gas from marine hydrate deposits are also considered in this report; on an IROR basis, it is $US2008 3.50-4.00/Mscf more expensive to produce marine hydrates than conventional marine gas assuming the existence of sufficiently large marine hydrate accumulations. While these prices represent the best available estimates, the economic evaluation of a specific project is highly dependent on the producibility of the target zone, the amount of gas in place, the associated geologic and depositional environment, existing pipeline infrastructure, and local tariffs and taxes. ?? 2009 Elsevier B.V.

  15. Natural gas hydrate in sediments imaged by cryogenic SEM: Insights from lab experiments on synthetic hydrates as interpretive guides.

    NASA Astrophysics Data System (ADS)

    Stern, L. A.; Kirby, S. H.

    2006-12-01

    In the investigation of natural gas hydrates, distinguishing in situ grain textures and microstructures from artifacts produced during retrieval, storage, and examination can be quite challenging. Using cryogenic scanning electron microscopy, we investigated the physical states of gas hydrates produced in our lab as well as of those in drill core of hydrate-bearing sediment from marine and Arctic permafrost environments. Here, we compare grain and pore structures observed in samples from the Cascadia margin (courtesy IODP Expedition 311), McKenzie River Delta (Mallik Well 5L-38), and Gulf of Mexico (RSV Marion Dufresne 2002), with those present in hydrocarbon hydrates grown in our laboratory and subjected to controlled P-T conditions. The following trends are apparent for the natural gas hydrates imaged to-date: (1) Samples typically contain massive domains of polycrystalline gas hydrate that in turn contain isolated gas-filled pores that are sometimes lined with euhedral hydrate crystals. Pores are typically 5 50 microns in diameter and occupy roughly 10-30 percent of the domain. Grain sizes, where visible, are commonly 20 to 50 microns. (2) Hydrate grain boundaries, particularly near the exposed sample surface, are often replaced by a nanoporous material. Based on its location and behavior, this material is presumed to be gas-charged porous ice produced by hydrate decomposition along grain surfaces. In some samples, grains are instead bounded by a framework of dense, tabular material embedded within the sample, best revealed upon sublimation of the hydrate. Their composition is yet unknown but may be salt or carbonate-bearing minerals. (3) Where hydrate grows into clayey sediments, the clays typically arrange with platelets subparallel around the pods or veins of hydrate. (4) Domains of nano-to-micro- porous water ice are also seen in all recovered natural samples, presumed to be hydrate decomposition product produced during drill-core retrieval and handling

  16. Thermodynamic stability, spectroscopic identification, and gas storage capacity of CO2-CH4-N2 mixture gas hydrates: implications for landfill gas hydrates.

    PubMed

    Lee, Hyeong-Hoon; Ahn, Sook-Hyun; Nam, Byong-Uk; Kim, Byeong-Soo; Lee, Gang-Woo; Moon, Donghyun; Shin, Hyung Joon; Han, Kyu Won; Yoon, Ji-Ho

    2012-04-03

    Landfill gas (LFG), which is primarily composed of CH(4), CO(2), and N(2), is produced from the anaerobic digestion of organic materials. To investigate the feasibility of the storage and transportation of LFG via the formation of hydrate, we observed the phase equilibrium behavior of CO(2)-CH(4)-N(2) mixture hydrates. When the specific molar ratio of CO(2)/CH(4) was 40/55, the equilibrium dissociation pressures were gradually shifted to higher pressures and lower temperatures as the mole fraction of N(2) increased. X-ray diffraction revealed that the CO(2)-CH(4)-N(2) mixture hydrate prepared from the CO(2)/CH(4)/N(2) (40/55/5) gas mixture formed a structure I clathrate hydrate. A combination of Raman and solid-state (13)C NMR measurements provided detailed information regarding the cage occupancy of gas molecules trapped in the hydrate frameworks. The gas storage capacity of LFG hydrates was estimated from the experimental results for the hydrate formations under two-phase equilibrium conditions. We also confirmed that trace amounts of nonmethane organic compounds do not affect the cage occupancy of gas molecules or the thermodynamic stability of LFG hydrates.

  17. Separation of SF6 from gas mixtures using gas hydrate formation.

    PubMed

    Cha, Inuk; Lee, Seungmin; Lee, Ju Dong; Lee, Gang-woo; Seo, Yongwon

    2010-08-15

    This study aims to examine the thermodynamic feasibility of separating sulfur hexafluoride (SF(6)), which is widely used in various industrial fields and is one of the most potent greenhouse gases, from gas mixtures using gas hydrate formation. The key process variables of hydrate phase equilibria, pressure-composition diagram, formation kinetics, and structure identification of the mixed gas hydrates, were closely investigated to verify the overall concept of this hydrate-based SF(6) separation process. The three-phase equilibria of hydrate (H), liquid water (L(W)), and vapor (V) for the binary SF(6) + water mixture and for the ternary N(2) + SF(6) + water mixtures with various SF(6) vapor compositions (10, 30, 50, and 70%) were experimentally measured to determine the stability regions and formation conditions of pure and mixed hydrates. The pressure-composition diagram at two different temperatures of 276.15 and 281.15 K was obtained to investigate the actual SF(6) separation efficiency. The vapor phase composition change was monitored during gas hydrate formation to confirm the formation pattern and time needed to reach a state of equilibrium. Furthermore, the structure of the mixed N(2) + SF(6) hydrate was confirmed to be structure II via Raman spectroscopy. Through close examination of the overall experimental results, it was clearly verified that highly concentrated SF(6) can be separated from gas mixtures at mild temperatures and low pressure conditions.

  18. Formation of Structured Water and Gas Hydrate by the Use of Xenon Gas in Vegetable Tissue

    NASA Astrophysics Data System (ADS)

    Ando, Hiroko; Suzuki, Toru; Kawagoe, Yoshinori; Makino, Yoshio; Oshita, Seiichi

    Freezing is a valuable technique for food preservation. However, vegetables are known to be softening remarkably after freezing and thawing process. It is expected to find alternative technique instead of freezing. Recently, the application of structured water and/or gas hydrate had been attempted to prolong the preservation of vegetable. In this study, the formation process of structure water and/or gas hydrate in pure water and carrot tissue was investigated by using NMR relaxation times, T1 and T2, of which applying condition was up to 0.4MPa and 0.8MPa at 5oC. Under the pressure of 0.4MPa, no gas hydrate was appeared, however, at 0.8MPa, formation of gas hydrate was recognized in both water and carrot tissue. Once the gas hydrate formation process in carrot tissue started, T1 and T2 increased remarkably. After that, as the gas hydrate developed, then T1 and T2 turned to decrease. Since this phenomenon was not observed in pure water, it is suggested that behavior of NMR relaxation time just after the formation of gas hydrate in carrot tissue may be peculiar to compartment system such as inter and intracellular spaces.

  19. Ocean Observatory Gas Hydrates Experiments on the Cascadia Margin

    NASA Astrophysics Data System (ADS)

    Scherwath, Martin; Heesemann, Martin; Mihaly, Steve; Kelley, Deborah; Moran, Kate; Philip, Brendan; Römer, Miriam; Riedel, Michael; Solomon, Evan; Thomsen, Laurenz; Purser, Autun

    2016-04-01

    Ocean Networks Canada's (ONC's) NEPTUNE observatory and the Ocean Observatories Initiative's (OOI's) Cabled Array installations enable long-term gas hydrate experiments on the Cascadia Margin offshore Vancouver Island and Washington and Oregon State. The great advantage of cabled ocean networks in providing power and high bandwidth internet access to the seafloor on a permanent basis is allowing constant monitoring and interacting with experiments hundreds of kilometres away from shore throughout the year. Many different gas hydrate related experiments are installed at three various hydrate nodes, Clayoquot Slope and Barkley Canyon offshore Vancouver Island and Southern Hydrate Ridge offshore Oregon. As an example, a seafloor crawler called Wally is operated from Bremen in Germany by Jacobs University, carrying out measurements by moving around the Barkley hydrate mounds on a daily basis, determining for instance the speed of dynamic changes of the benthic communities. In another example, several years of hourly sonar data show gas bubbles rising from the seafloor near the Bullseye Vent with varying intensities, allowing statistically sound correlations with other seafloor parameters such as ground shaking, temperature and pressure variations and currents, where tidal pressure appearing as the main driver. The Southern Hydrate Ridge is now equipped with the world's first long-term seafloor mass spectrometer, co-located with a camera and lights, hydrophone, current meters, pressure sensor, autonomous OSMO and fluid samplers, and is surrounded by a seismometer array for local seismicity. The data are freely available through open access data portals at: http://dmas.uvic.ca/home and https://ooinet.oceanobservatories.org/

  20. Gas Production from Hydrate-Bearing Sediments - Emergent Phenomena -

    SciTech Connect

    Jung, J.W.; Jang, J.W.; Tsouris, Costas; Phelps, Tommy Joe; Rawn, Claudia J; Santamarina, Carlos

    2012-01-01

    Even a small fraction of fine particles can have a significant effect on gas production from hydrate-bearing sediments and sediment stability. Experiments were conducted to investigate the role of fine particles on gas production using a soil chamber that allows for the application of an effective stress to the sediment. This chamber was instrumented to monitor shear-wave velocity, temperature, pressure, and volume change during CO{sub 2} hydrate formation and gas production. The instrumented chamber was placed inside the Oak Ridge National Laboratory Seafloor Process Simulator (SPS), which was used to control the fluid pressure and temperature. Experiments were conducted with different sediment types and pressure-temperature histories. Fines migrated within the sediment in the direction of fluid flow. A vuggy structure formed in the sand; these small cavities or vuggs were precursors to the development of gas-driven fractures during depressurization under a constant effective stress boundary condition. We define the critical fines fraction as the clay-to-sand mass ratio when clays fill the pore space in the sand. Fines migration, clogging, vugs, and gas-driven fracture formation developed even when the fines content was significantly lower than the critical fines fraction. These results show the importance of fines in gas production from hydrate-bearing sediments, even when the fines content is relatively low.

  1. Simulation of gas hydrate dissociation caused by repeated tectonic uplift events

    NASA Astrophysics Data System (ADS)

    Goto, Shusaku; Matsubayashi, Osamu; Nagakubo, Sadao

    2016-05-01

    Gas hydrate dissociation by tectonic uplift is often used to explain geologic and geophysical phenomena, such as hydrate accumulation probably caused by hydrate recycling and the occurrence of double bottom-simulating reflectors in tectonically active areas. However, little is known of gas hydrate dissociation resulting from tectonic uplift. This study investigates gas hydrate dissociation in marine sediments caused by repeated tectonic uplift events using a numerical model incorporating the latent heat of gas hydrate dissociation. The simulations showed that tectonic uplift causes upward movement of some depth interval of hydrate-bearing sediment immediately above the base of gas hydrate stability (BGHS) to the gas hydrate instability zone because the sediment initially maintains its temperature: in that interval, gas hydrate dissociates while absorbing heat; consequently, the temperature of the interval decreases to that of the hydrate stability boundary at that depth. Until the next uplift event, endothermic gas hydrate dissociation proceeds at the BGHS using heat mainly supplied from the sediment around the BGHS, lowering the temperature of that sediment. The cumulative effects of these two endothermic gas hydrate dissociations caused by repeated uplift events lower the sediment temperature around the BGHS, suggesting that in a marine area in which sediment with a highly concentrated hydrate-bearing layer just above the BGHS has been frequently uplifted, the endothermic gas hydrate dissociation produces a gradual decrease in thermal gradient from the seafloor to the BGHS. Sensitivity analysis for model parameters showed that water depth, amount of uplift, gas hydrate saturation, and basal heat flow strongly influence the gas hydrate dissociation rate and sediment temperature around the BGHS.

  2. New Natural Gas Storage and Transportation Capabilities Utilizing Rapid Methane Hydrate Formation Techniques

    SciTech Connect

    Brown, T.D.; Taylor, C.E.; Bernardo, M.

    2010-01-01

    Natural gas (methane as the major component) is a vital fossil fuel for the United States and around the world. One of the problems with some of this natural gas is that it is in remote areas where there is little or no local use for the gas. Nearly 50 percent worldwide natural gas reserves of ~6,254.4 trillion ft3 (tcf) is considered as stranded gas, with 36 percent or ~86 tcf of the U.S natural gas reserves totaling ~239 tcf, as stranded gas [1] [2]. The worldwide total does not include the new estimates by U.S. Geological Survey of 1,669 tcf of natural gas north of the Arctic Circle, [3] and the U.S. ~200,000 tcf of natural gas or methane hydrates, most of which are stranded gas reserves. Domestically and globally there is a need for newer and more economic storage, transportation and processing capabilities to deliver the natural gas to markets. In order to bring this resource to market, one of several expensive methods must be used: 1. Construction and operation of a natural gas pipeline 2. Construction of a storage and compression facility to compress the natural gas (CNG) at 3,000 to 3,600 psi, increasing its energy density to a point where it is more economical to ship, or 3. Construction of a cryogenic liquefaction facility to produce LNG, (requiring cryogenic temperatures at <-161 °C) and construction of a cryogenic receiving port. Each of these options for the transport requires large capital investment along with elaborate safety systems. The Department of Energy's Office of Research and Development Laboratories at the National Energy Technology Laboratory (NETL) is investigating new and novel approaches for rapid and continuous formation and production of synthetic NGHs. These synthetic hydrates can store up to 164 times their volume in gas while being maintained at 1 atmosphere and between -10 to -20°C for several weeks. Owing to these properties, new process for the economic storage and transportation of these synthetic hydrates could be envisioned

  3. Are seafloor pockmarks on the Chatham Rise, New Zealand, linked to CO2 hydrates? Gas hydrate stability considerations.

    NASA Astrophysics Data System (ADS)

    Pecher, I. A.; Davy, B. W.; Rose, P. S.; Coffin, R. B.

    2015-12-01

    Vast areas of the Chatham Rise east of New Zealand are covered by seafloor pockmarks. Pockmark occurrence appears to be bathymetrically controlled with a band of smaller pockmarks covering areas between 500 and 700 m and large seafloor depressions beneath 800 m water depth. The current depth of the top of methane gas hydrate stability in the ocean is about 500 m and thus, we had proposed that pockmark formation may be linked to methane gas hydrate dissociation during sealevel lowering. However, while seismic profiles show strong indications of fluid flow, geochemical analyses of piston cores do not show any evidence for current or past methane flux. The discovery of Dawsonite, indicative of significant CO2 flux, in a recent petroleum exploration well, together with other circumstantial evidence, has led us to propose that instead of methane hydrate, CO2 hydrate may be linked to pockmark formation. We here present results from CO2 hydrate stability calculations. Assuming water temperature profiles remain unchanged, we predict the upper limit of pockmark occurrence to coincide with the top of CO2 gas hydrate stability during glacial-stage sealevel lowstands. CO2 hydrates may therefore have dissociated during sealevel lowering leading to gas escape and pockmark formation. In contrast to our previous model linking methane hydrate dissociation to pockmark formation, gas hydrates would dissociate beneath a shallow base of CO2 hydrate stability, rather than on the seafloor following upward "grazing" of the top of methane hydrate stability. Intriguingly, at the water depths of the larger seafloor depressions, the base of gas hydrate stability delineates the phase boundary between CO2 hydrates and super-saturated CO2. We caution that because of the high solubility of CO2, dissociation from hydrate to free gas or super-saturated CO2 would imply high concentrations of CO2 and speculate that pockmark formation may be linked to CO2 hydrate dissolution rather than dissociation

  4. Probable Occurrence of Gas Hydrates Along the Continental Margins of India

    NASA Astrophysics Data System (ADS)

    Ramprasad, T.

    2004-12-01

    The gas hydrates have gained the importance of being potential to be an alternate energy resource and are know to occur world wide in the sediments of the outer continental margins and polar regions associated with permafrost and are stable under certain temperature-pressure conditions. A gas hydrate stability zone (GHSZ) thickness map of Indian offshore has been created from spatial analysis of physical parameters that influence the formation and preservation of gas hydrates by using Arc/Info GIS software. These parameters include bathymetry and heatflow/geothermal gradient data obtained from published literature, digital databases and unpublished sources, and the seabed temperature from extrapolation of the best-fit polynomial of hydrothermal profile. In addition to the measured heatflow/geothermal data, the values were predicted in the regions devoid of data by considering the Indian offshore comprising of three provinces such as: oceanic, stretched continental crust and the crust influenced by the hotspot. Heatflow versus age relationship is used in case of oceanic crust in Arabian Sea, Bay of Bengal, and Andaman Sea in the regions beyond the shelf edge. The stretched crust criterion is applied only in the northern Arabian Sea between shelf and the inferred oceanic crust. A regression line is fitted between the available heatflow data and the corresponding age of the crust to compute heatflow values, in the region where the crust influenced by the Reunion hotspot. Seabed temperature data were also predicted in deficient areas based on the regression analysis of available bathymetry versus seabed temperature relationship. The thickness of gas hydrate stability zone was computed both in TWT (msec) and meters, by solving the gas hydrate phase and pressure-temperature equations at each GIS grid node. The GHSZ thickness map is reliable to the extent it can be used as an important indicator for gas hydrate potential of an area. Large volumes of multi-channel seismic

  5. Gas hydrates in the Messoyakha gas field of the West Siberian Basin - a re-examination of the geologic evidence

    USGS Publications Warehouse

    Collett, Timothy S.; Ginsburg, Gabriel D.; ,

    1997-01-01

    The amount of natural gas within the gas hydrate accumulations of the world is believed to greatly exceed the volume of known conventional natural gas reserves. The hydrocarbon production history of the Russian Messoyakha field, located in the West Siberian Basin, has been used as evidence that gas hydrates are an immediate source of natural gas that can be produced by conventional means. Re-examination of available geologic, geochemical, and hydrocarbon production data suggests, however, that gas hydrates may not have contributed to gas production in the Messoyakha field. More field and laboratory studies are needed to assess the historical contribution of gas hydrate production in the Messoyakha field.

  6. Three types of gas hydrate reservoirs in the Gulf of Mexico identified in LWD data

    USGS Publications Warehouse

    Lee, Myung Woong; Collett, Timothy S.

    2011-01-01

    High quality logging-while-drilling (LWD) well logs were acquired in seven wells drilled during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II in the spring of 2009. These data help to identify three distinct types of gas hydrate reservoirs: isotropic reservoirs in sands, vertical fractured reservoirs in shale, and horizontally layered reservoirs in silty shale. In general, most gas hydratebearing sand reservoirs exhibit isotropic elastic velocities and formation resistivities, and gas hydrate saturations estimated from the P-wave velocity agree well with those from the resistivity. However, in highly gas hydrate-saturated sands, resistivity-derived gas hydrate-saturation estimates appear to be systematically higher by about 5% over those estimated by P-wave velocity, possibly because of the uncertainty associated with the consolidation state of gas hydrate-bearing sands. Small quantities of gas hydrate were observed in vertical fractures in shale. These occurrences are characterized by high formation resistivities with P-wave velocities close to those of water-saturated sediment. Because the formation factor varies significantly with respect to the gas hydrate saturation for vertical fractures at low saturations, an isotropic analysis of formation factor highly overestimates the gas hydrate saturation. Small quantities of gas hydrate in horizontal layers in shale are characterized by moderate increase in P-wave velocities and formation resistivities and either measurement can be used to estimate gas hydrate saturations.

  7. Methane and carbon dioxide hydrates on Mars: Potential origins, distribution, detection, and implications for future in situ resource utilization

    NASA Astrophysics Data System (ADS)

    Pellenbarg, Robert E.; Max, Michael D.; Clifford, Stephen M.

    2003-04-01

    There is high probability for the long-term crustal accumulation of methane and carbon dioxide on Mars. These gases can arise from a variety of processes, including deep biosphere activity and abiotic mechanisms, or, like water, they could exist as remnants of planetary formation and by-products of internal differentiation. CH4 and CO2 would tend to rise buoyantly toward the planet's surface, condensing with water under appropriate conditions of temperature and pressure to form gas hydrate. Gas hydrates are a class of materials created when gas molecules are trapped within a crystalline lattice of water-ice. The hydrate stability fields of both CH4 and CO2 encompass a portion of the Martian crust that extends from within the water-ice cryosphere, from a depth as shallow as ~10-20 m to as great as a kilometer or more below the base of the Martian cryosphere. The presence and distribution of methane and carbon dioxide hydrates may be of critical importance in understanding the geomorphic evolution of Mars and the geophysical identification of water and other volatiles stored in the hydrates. Of critical importance, Martian gas hydrates would ensure the availability of key in situ resources for sustaining future robotic and human exploration, and the eventual colonization, of Mars.

  8. Potential role of gas hydrate decomposition in generating submarine slope failures: Chapter 12

    USGS Publications Warehouse

    Pauli, Charles K.; mUssler, William III; Dillon, William P.; Max, Michael D.

    2003-01-01

    Gas hydrate decomposition is hypothesized to be a factor in generating weakness in continental margin sediments that may help explain some of the observed patterns of continental margin sediment instability. The processes associated with formation and decomposition of gas hydrate can cause the strengthening of sediments in which gas hydrate grow and the weakening of sediments in which gas hydrate decomposes. The weakened sediments may form horizons along which the potential for sediment failure is increased. While a causal relationship between slope failures and gas hydrate decomposition has not been proven, a number of empirical observations support their potential connection.

  9. Gas hydrates from the continental slope, offshore Sakhalin Island, Okhotsk Sea

    USGS Publications Warehouse

    Ginsburg, G.D.; Soloviev, V.A.; Cranston, R.E.; Lorenson, T.D.; Kvenvolden, K.A.

    1993-01-01

    Ten gas-vent fields were discovered in the Okhotsk Sea on the northeast continental slope offshore from Sakhalin Island in water depths of 620-1040 m. At one vent field, estimated to be more than 250 m across, gas hydrates, containing mainly microbial methane (??13C = -64.3???), were recovered from subbottom depths of 0.3-1.2 m. The sediment, having lenses and bedded layers of gas hydrate, contained 30-40% hydrate per volume of wet sediment. Although gas hydrates were not recovered at other fields, geochemical and thermal measurements suggest that gas hydrates are present. ?? 1993 Springer-Verlag.

  10. Gas content and composition of gas hydrate from sediments of the southeastern North American continental margin

    USGS Publications Warehouse

    Lorenson, T.D.; Collett, T.S.

    2000-01-01

    Gas hydrate samples were recovered from four sites (Sites 994, 995, 996, and 997) along the crest of the Blake Ridge during Ocean Drilling Program (ODP) Leg 164. At Site 996, an area of active gas venting, pockmarks, and chemosynthetic communities, vein-like gas hydrate was recovered from less than 1 meter below seafloor (mbsf) and intermittently through the maximum cored depth of 63 mbsf. In contrast, massive gas hydrate, probably fault filling and/or stratigraphically controlled, was recovered from depths of 260 mbsf at Site 994, and from 331 mbsf at Site 997. Downhole-logging data, along with geochemical and core temperature profiles, indicate that gas hydrate at Sites 994, 995, and 997 occurs from about 180 to 450 mbsf and is dispersed in sediment as 5- to 30-m-thick zones of up to about 15% bulk volume gas hydrate. Selected gas hydrate samples were placed in a sealed chamber and allowed to dissociate. Evolved gas to water volumetric ratios measured on seven samples from Site 996 ranged from 20 to 143 mL gas/mL water to 154 mL gas/mL water in one sample from Site 994, and to 139 mL gas/mL water in one sample from Site 997, which can be compared to the theoretical maximum gas to water ratio of 216. These ratios are minimum gas/water ratios for gas hydrate because of partial dissociation during core recovery and potential contamination with pore waters. Nonetheless, the maximum measured volumetric ratio indicates that at least 71% of the cages in this gas hydrate were filled with gas molecules. When corrections for pore-water contamination are made, these volumetric ratios range from 29 to 204, suggesting that cages in some natural gas hydrate are nearly filled. Methane comprises the bulk of the evolved gas from all sites (98.4%-99.9% methane and 0%-1.5% CO2). Site 996 hydrate contained little CO2 (0%-0.56%). Ethane concentrations differed significantly from Site 996, where they ranged from 720 to 1010 parts per million by volume (ppmv), to Sites 994 and 997

  11. Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water with Secondary Guests

    SciTech Connect

    Cha, Jong-Ho; Seol, Yongkoo

    2013-10-07

    We suggest a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. The hydrate formation reactions were carried out in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water (8.95 wt % salinity) mixed with the hydrate formers shows an increased upper temperature limit from -2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate turned out to be similar to that with simple CO2 hydrate at the upper temperature limit. Hydrate formation rates (Rf) for the double hydrates with CP and CH are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energy efficiency of the double hydrate system for the desalination process. Dissociated water from the hydrates shows greater than 90% salt removal efficiency for the hydrates with the secondary guests, which is also improved from about 70% salt removal efficiency for the simple hydrates.

  12. Evaluation of the geological relationships to gas hydrate formation and stability

    SciTech Connect

    Not Available

    1985-01-01

    During the reported year we have enhanced our knowledge on and gained considerable experience in assessment of the gas hydrate resources in the offshore environments. Specifically, we have learned and gained experience in the following: Efficiently locating data sources, including published literature and unpublished information. We have established personal communication extremely critical in data accessability and acquisition. We have updated information pertinent to gas hydrate knowledge, also based on thorough study and evaluation of most Russian literature and additional publications in languages other than English. Besides critical evaluation of widely spread literature, in many cases our reports include previously unpublished information (e.g. BSRs from the Gulf of Mexico). The assessment of the gas resources potential associated with the gas hydrates, although in most cases at a low level of confidence, appears also very encouraging for further, more detailed, study. We are also confident that, because of the present reports' format, new data and a concept-oriented approach, the result of our study will be of strong interest to various industries, research institutions and numerous governmental agencies.

  13. Forming factors of gas hydrate chimney in the Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Hyo; Chun, Jong-Hwa; Koo, Nam-Hyng; Kim, Won-Sik; Lee, Ho-Young; Lee, Joo-Yong

    2016-04-01

    Seismic chimneys ranging in width from 200 m to 1,000 m are observed in the seismic sections obtained in the Ulleung Basin, East Sea. In consequence of Ulleung Basin Gas Hydrate Expedition 1 and 2, concentrations of gas hydrates were identified. Especially, 6 chimney sites were drilled and the occurrence of gas hydrate was identified at all wells. Through the interpreting seismic section, three factors affect the formation of gas hydrate chimney; mass transport deposit, fault, igneous intrusion. These three factors result in three case of forming gas hydrate chimney. Firstly, gas hydrate chimney appears predominantly in the fault zone. Deep-rooted fault reach to mass transport deposit and gas hydrate chimney which is mostly rooted in mass transport deposit is formed. Secondly, Gas hydrate chimney appears linked to igneous intrusion. Igneous intrusion result in forming fault in overlying strata. Similar to first case, this fault traverses mass transport deposit and gas hydrate chimney rooted in mass transport deposit is created. Thirdly, gas hydrate chimney is formed at thick mass transport deposit without fault. In this case, chimney is not reach to seabed in contrast with first and second case. The thickness of mass transport deposit is 0.2 second in two-way travel times. Overburden load cause to pressure at the upper part of mass transport deposit. This leads to fracture in overlying sediments and form gas hydrate chimney.

  14. Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

    USGS Publications Warehouse

    Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

    2011-01-01

    During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

  15. Stabilization of methane hydrate by pressurization with He or N2 gas.

    PubMed

    Lu, Hailong; Tsuji, Yoshihiro; Ripmeester, John A

    2007-12-27

    The behavior of methane hydrate was investigated after it was pressurized with helium or nitrogen gas in a test system by monitoring the gas compositions. The results obtained indicate that even when the partial pressure of methane gas in such a system is lower than the equilibrium pressure at a certain temperature, the dissociation rate of methane hydrate is greatly depressed by pressurization with helium or nitrogen gas. This phenomenon is only observed when the total pressure of methane and helium (or nitrogen) gas in the system is greater than the equilibrium pressure required to stabilize methane hydrate with just methane gas. The following model has been proposed to explain the observed phenomenon: (1) Gas bubbles develop at the hydrate surface during hydrate dissociation, and there is a pressure balance between the methane gas inside the gas bubbles and the external pressurizing gas (methane and helium or nitrogen), as transmitted through the water film; as a result the methane gas in the gas bubbles stabilizes the hydrate surface covered with bubbles when the total gas pressure is greater than the equilibrium pressure of the methane hydrate at that temperature; this situation persists until the gas in the bubbles becomes sufficiently dilute in methane or until the surface becomes bubble-free. (2) In case of direct contact of methane hydrate with water, the water surrounding the hydrate is supersaturated with methane released upon hydrate dissociation; consequently, methane hydrate is stabilized when the hydrostatic pressure is above the equilibrium pressure of methane hydrate at a certain temperature, again until the dissolved gas at the surface becomes sufficiently dilute in methane. In essence, the phenomenon is due to the presence of a nonequilibrium state where there is a chemical potential gradient from the solid hydrate particles to the bulk solution that exists as long as solid hydrate remains.

  16. Estimating pore-space gas hydrate saturations from well log acoustic data

    USGS Publications Warehouse

    Lee, Myung W.; Waite, William F.

    2008-01-01

    Relating pore-space gas hydrate saturation to sonic velocity data is important for remotely estimating gas hydrate concentration in sediment. In the present study, sonic velocities of gas hydrate–bearing sands are modeled using a three-phase Biot-type theory in which sand, gas hydrate, and pore fluid form three homogeneous, interwoven frameworks. This theory is developed using well log compressional and shear wave velocity data from the Mallik 5L-38 permafrost gas hydrate research well in Canada and applied to well log data from hydrate-bearing sands in the Alaskan permafrost, Gulf of Mexico, and northern Cascadia margin. Velocity-based gas hydrate saturation estimates are in good agreement with Nuclear Magneto Resonance and resistivity log estimates over the complete range of observed gas hydrate saturations.

  17. High-resolution seismic imaging of the gas and gas hydrate system at Green Canyon 955 in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Collett, T. S.; Shedd, W. W.; Frye, M.

    2015-12-01

    High-resolution 2D seismic data acquired by the USGS in 2013 enable detailed characterization of the gas and gas hydrate system at lease block Green Canyon 955 (GC955) in the Gulf of Mexico, USA. Earlier studies, based on conventional industry 3D seismic data and logging-while-drilling (LWD) borehole data acquired in 2009, identified general aspects of the regional and local depositional setting along with two gas hydrate-bearing sand reservoirs and one layer containing fracture-filling gas hydrate within fine-grained sediments. These studies also highlighted a number of critical remaining questions. The 2013 high-resolution 2D data fill a significant gap in our previous understanding of the site by enabling interpretation of the complex system of faults and gas chimneys that provide conduits for gas flow and thus control the gas hydrate distribution observed in the LWD data. In addition, we have improved our understanding of the main channel/levee sand reservoir body, mapping in fine detail the levee sequences and the fault system that segments them into individual reservoirs. The 2013 data provide a rarely available high-resolution view of a levee reservoir package, with sequential levee deposits clearly imaged. Further, we can calculate the total gas hydrate resource present in the main reservoir body, refining earlier estimates. Based on the 2013 seismic data and assumptions derived from the LWD data, we estimate an in-place volume of 840 million cubic meters or 29 billion cubic feet of gas in the form of gas hydrate. Together, these interpretations provide a significantly improved understanding of the gas hydrate reservoirs and the gas migration system at GC955.

  18. Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Stern, Laura A.; Lorenson, T.D.; Pinkston, John C.

    2011-01-01

    Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA–DOE–USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5 m to 760.1 m depth, and sections investigated here were retrieved from 619.9 m and 661.0 m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70–75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20–120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas.

  19. Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Stern, L.A.; Lorenson, T.D.; Pinkston, J.C.

    2011-01-01

    Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5. m to 760.1. m depth, and sections investigated here were retrieved from 619.9. m and 661.0. m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70-75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20-120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas. ?? 2009.

  20. Gas geochemistry of the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: implications for gas hydrate exploration in the Arctic

    USGS Publications Warehouse

    Lorenson, T.D.; Collett, T.S.; Hunter, R.B.

    2011-01-01

    Gases were analyzed from well cuttings, core, gas hydrate, and formation tests at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well, drilled within the Milne Point Unit, Alaska North Slope. The well penetrated a portion of the Eileen gas hydrate deposit, which overlies the more deeply buried Prudhoe Bay, Milne Point, West Sak, and Kuparuk River oil fields. Gas sources in the upper 200 m are predominantly from microbial sources (C1 isotopic compositions ranging from −86.4 to −80.6‰). The C1 isotopic composition becomes progressively enriched from 200 m to the top of the gas hydrate-bearing sands at 600 m. The tested gas hydrates occur in two primary intervals, units D and C, between 614.0 m and 664.7 m, containing a total of 29.3 m of gas hydrate-bearing sands. The hydrocarbon gases in cuttings and core samples from 604 to 914 m are composed of methane with very little ethane. The isotopic composition of the methane carbon ranges from −50.1 to −43.9‰ with several outliers, generally decreasing with depth. Gas samples collected by the Modular Formation Dynamics Testing (MDT) tool in the hydrate-bearing units were similarly composed mainly of methane, with up to 284 ppm ethane. The methane isotopic composition ranged from −48.2 to −48.0‰ in the C sand and from −48.4 to −46.6‰ in the D sand. Methane hydrogen isotopic composition ranged from −238 to −230‰, with slightly more depleted values in the deeper C sand. These results are consistent with the concept that the Eileen gas hydrates contain a mixture of deep-sourced, microbially biodegraded thermogenic gas, with lesser amounts of thermogenic oil-associated gas, and coal gas. Thermal gases are likely sourced from existing oil and gas accumulations that have migrated up-dip and/or up-fault and formed gas hydrate in response to climate cooling with permafrost formation.

  1. Selective Encaging of N2O in N2O-N2 Binary Gas Hydrates via Hydrate-Based Gas Separation.

    PubMed

    Yang, Youjeong; Shin, Donghoon; Choi, Seunghyun; Woo, Yesol; Lee, Jong-Won; Kim, Dongseon; Shin, Hee-Young; Cha, Minjun; Yoon, Ji-Ho

    2017-02-22

    The crystal structure and guest inclusion behaviors of nitrous oxide-nitrogen (N2O-N2) binary gas hydrates formed from N2O/N2 gas mixtures are determined through spectroscopic analysis. Powder X-ray diffraction results indicate that the crystal structure of all the N2O-N2 binary gas hydrates is identified as the structure I (sI) hydrate. Raman spectra for N2O-N2 binary gas hydrate formed from N2O/N2 (80/20, 60/40, 40/60 mol %) gas mixtures reveal that N2O molecules occupy both large and small cages of the sI hydrate. In contrast, there is a single Raman band of N2O molecules for N2O-N2 binary gas hydrate formed from N2O/N2 (20/80 mol %) gas mixture, indicating that N2O molecules are trapped in only large cages of sI hydrate. From temperature-dependent Raman spectra and the Predictive Soave-Redlich-Kwong (PSRK) model calculation, we confirm the self-preservation of N2O-N2 binary gas hydrates in the temperature range of 210-270 K. Both the experimental measurements and the PSRK model calculations demonstrate the preferential occupation of N2O molecules rather than N2 molecules in the hydrate cages, leading to a possible process for separating N2O from gas mixtures via hydrate formation. The phase equilibrium conditions, pseudo pressure-composition (P-x) diagram, and gas storage capacity of N2O-N2 binary gas hydrates are discussed in detail.

  2. [Determination of tracer gas contents in sediment pore water of gas hydrate area by two-dimensional gas chromatography].

    PubMed

    Wang, Hu; Yang, Qunhui; Ji, Fuwu; Zhou, Huaiyang; Xue, Xiang

    2011-01-01

    A two-dimensional gas chromatographic instrument was established by the capillary flow technology (Deans Switch) and two columns (PoraPLOT Q and Molsieve 5A) and three detectors (pulsed discharge helium ionization detector, flame photometric detector and thermal conductivity detector). The instrument can be used to measure tracer gases simultaneously including hydrogen, methane, carbon dioxide and hydrogen sulfide. The detection limits of the hydrogen, methane, carbon dioxide and hydrogen sulfide were 0.51, 0.17, 82 and 0.08 micromol/mol, and the calibration curves presented good linear relationships in the range of 2-1030, 0.6-501, 120-10500 and 0.2- 49.1 micromol/mol, respectively. The relative standard deviations were less than 10% for the measurements of ten standard gases. By this method, the tracer gases in the sediment pore water of gas hydrate area in South China Sea had been detected. This method is simple, sensitive, and suitable for on-board detection. Compared with the usual methods for measuring tracer gases, the amount of a sample necessary is reduced greatly. It is useful for the survey of gas hydrate and hydrothermal resources below sea floor and for the research of dissolved gases in the ocean.

  3. Natural gas hydrate occurrence and issues: Large amounts of methane in gas hydrates are potential energy sources; role in climate change?

    SciTech Connect

    Kvenvolden, K.

    1995-09-01

    Naturally occurring gas hydrate is a solid, icelike substance composed of rigid cages of water molecules that enclose molecules of gas, mainly methane. Chemically, this substance is a water clathrate of methane, often called methane clathrate, in addition to methane hydrate or gas hydrate. In an ideally saturated methane hydrate, the molar ratio of methane to water is 1:5.75, that is, equal to a volumetric ratio at standard conditions of about 164:1. Gas hydrate deposits aaoccur under specific conditions of pressure and temperature, where the supply of methane is sufficient to initiate and stabilize the hydrate structure. These conditions are met on Earth in shallow sediment, less than 2,000 meters deep in two regions: (1) continental, including continental shelves at high latitudes where surface temperatures are very cold, and (2) submarine continental slopes and rises where not only is the bottom water cold but also pressures are very high. Thus in polar regions, gas hydrate is found where temperatures are cold enough for onshore and offshore permafrost to be present. During global warming, deep sea gas hydrates become more stable, but gas hydrate of polar continents and continental shelves is destabilized, leading to methane release over long time scales. Methane reaching the atmosphere from these sources contributes to the global warming trend. During a global cooling cycle, the whole system reverses. Methodologies are being developed to recover methane from this substance. Three principal methods are being considered: thermal stimulation, depressurization, and inhibitor injection.

  4. An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

    USGS Publications Warehouse

    Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

    2006-01-01

    The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

  5. The connection between natural gas hydrate and bottom-simulating reflectors

    NASA Astrophysics Data System (ADS)

    Majumdar, Urmi; Cook, Ann E.; Shedd, William; Frye, Matthew

    2016-07-01

    Bottom-simulating reflectors (BSRs) on marine seismic data are commonly used to identify the presence of natural gas hydrate in marine sediments, although the exact relationship between gas hydrate and BSRs is undefined. To clarify this relationship we compile a data set of probable gas hydrate occurrence as appraised from well logs of 788 industry wells in the northern Gulf of Mexico. We combine the well log data set with a data set of BSR distribution in the same area identified from 3-D seismic data. We find that a BSR increases the chances of finding gas hydrate by 2.6 times as opposed to drilling outside a BSR and that the wells within a BSR also contain thicker and higher resistivity hydrate accumulations. Even so, over half of the wells drilled through BSRs have no detectable gas hydrate accumulations and gas hydrate occurrences and BSRs do not coincide in most cases.

  6. CHARACTERIZING NATURAL GAS HYDRATES IN THE DEEP WATER GULF OF MEXICO: APPLICATIONS FOR SAFE EXPLORATION AND PRODUCTION ACTIVITIES

    SciTech Connect

    Steve Holditch; Emrys Jones

    2003-01-01

    In 2000, Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deepwater portions of the Gulf of Mexico. A Joint Industry Participation (JIP) group was formed in 2001, and a project partially funded by the U.S. Department of Energy (DOE) began in October 2001. The primary objective of this project is to develop technology and data to assist in the characterization of naturally occurring gas hydrates in the deep water Gulf of Mexico (GOM). These naturally occurring gas hydrates can cause problems relating to drilling and production of oil and gas, as well as building and operating pipelines. Other objectives of this project are to better understand how natural gas hydrates can affect seafloor stability, to gather data that can be used to study climate change, and to determine how the results of this project can be used to assess if and how gas hydrates act as a trapping mechanism for shallow oil or gas reservoirs. During April-September 2002, the JIP concentrated on: Reviewing the tasks and subtasks on the basis of the information generated during the three workshops held in March and May 2002; Writing Requests for Proposals (RFPs) and Cost, Time and Resource (CTRs) estimates to accomplish the tasks and subtasks; Reviewing proposals sent in by prospective contractors; Selecting four contractors; Selecting six sites for detailed review; and Talking to drill ship owners and operators about potential work with the JIP.

  7. Subsurface gas hydrates in the northern Gulf of Mexico

    USGS Publications Warehouse

    Boswell, Ray; Collett, Timothy S.; Frye, Matthew; Shedd, William; McConnell, Daniel R.; Shelander, Dianna

    2012-01-01

    The northernGulf of Mexico (GoM) has long been a focus area for the study of gashydrates. Throughout the 1980s and 1990s, work focused on massive gashydrates deposits that were found to form at and near the seafloor in association with hydrocarbon seeps. However, as global scientific and industrial interest in assessment of the drilling hazards and resource implications of gashydrate accelerated, focus shifted to understanding the nature and abundance of "buried" gashydrates. Through 2005, despite the drilling of more than 1200 oil and gas industry wells through the gashydrate stability zone, published evidence of significant sub-seafloor gashydrate in the GoM was lacking. A 2005 drilling program by the GoM GasHydrate Joint Industry Project (the JIP) provided an initial confirmation of the occurrence of gashydrates below the GoM seafloor. In 2006, release of data from a 2003 industry well in Alaminos Canyon 818 provided initial documentation of gashydrate occurrence at high concentrations in sand reservoirs in the GoM. From 2006 to 2008, the JIP facilitated the integration of geophysical and geological data to identify sites prospective for gashydrate-bearing sands, culminating in the recommendation of numerous drilling targets within four sites spanning a range of typical deepwater settings. Concurrent with, but independent of, the JIP prospecting effort, the Bureau of Ocean Energy Management (BOEM) conducted a preliminary assessment of the GoM gashydratepetroleum system, resulting in an estimate of 607 trillion cubic meters (21,444 trillion cubic feet) gas-in-place of which roughly one-third occurs at expected high concentrations in sand reservoirs. In 2009, the JIP drilled seven wells at three sites, discovering gashydrate at high saturation in sand reservoirs in four wells and suspected gashydrate at low to moderate saturations in two other wells. These results provide an initial confirmation of the complex nature and occurrence of gashydrate-bearing sands in

  8. Quantifying Hydrate Formation in Gas-rich Environments Using the Method of Characteristics

    NASA Astrophysics Data System (ADS)

    You, K.; Flemings, P. B.; DiCarlo, D. A.

    2015-12-01

    Methane hydrates hold a vast amount of methane globally, and have huge energy potential. Methane hydrates in gas-rich environments are the most promising production targets. We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation in such environments (Figure 1). Our solution shows that hydrate saturation is constant with time and space in a homogeneous system. Hydrate saturation is controlled by the initial thermodynamic condition of the system, and changed by the gas fractional flow. Hydrate saturation increases with the initial distance from the hydrate phase boundary. Different gas fractional flows behind the hydrate solidification front lead to different gas saturations at the hydrate solidification front. The higher the gas saturation at the front, the less the volume available to be filled by hydrate, and hence the lower the hydrate saturation. The gas fractional flow depends on the relative permeability curves, and the forces that drive the flow. Viscous forces (the drive for flow induced from liquid pressure gradient) dominate the flow, and hydrate saturation is independent on the gas supply rates and the flow directions at high gas supply rates. Hydrate saturation can be estimated as one minus the ratio of the initial to equilibrium salinity. Gravity forces (the drive for flow induced from the gravity) dominate the flow, and hydrate saturation depends on the flow rates and the flow directions at low gas supply rates. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with the flow rate for upward flow, and increases with the flow rate for downward flow. This analytical solution illuminates how hydrate is formed by gas (methane, CO2, ethane, propane) flowing into brine-saturated sediments at both the laboratory and geological scales (Figure 1). It provides an approach to generalize the understanding of hydrate solidification in gas

  9. Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems

    DOE PAGES

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

    2017-02-07

    The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

  10. Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Falenty, Andrzej; Chaouachi, Marwen; Haberthür, David; Kuhs, Werner F.

    2016-09-01

    In-situ synchrotron X-ray computed microtomography with sub-micrometer voxel size was used to study the decomposition of gas hydrates in a sedimentary matrix. Xenon-hydrate was used instead of methane hydrate to enhance the absorption contrast. The microstructural features of the decomposition process were elucidated indicating that the decomposition starts at the hydrate-gas interface; it does not proceed at the contacts with quartz grains. Melt water accumulates at retreating hydrate surface. The decomposition is not homogeneous and the decomposition rates depend on the distance of the hydrate surface to the gas phase indicating a diffusion-limitation of the gas transport through the water phase. Gas is found to be metastably enriched in the water phase with a concentration decreasing away from the hydrate-water interface. The initial decomposition process facilitates redistribution of fluid phases in the pore space and local reformation of gas hydrates. The observations allow also rationalizing earlier conjectures from experiments with low spatial resolutions and suggest that the hydrate-sediment assemblies remain intact until the hydrate spacers between sediment grains finally collapse; possible effects on mechanical stability and permeability are discussed. The resulting time resolved characteristics of gas hydrate decomposition and the influence of melt water on the reaction rate are of importance for a suggested gas recovery from marine sediments by depressurization.

  11. Depressurization-induced gas production from Class 1 and Class 2hydrate deposits

    SciTech Connect

    Moridis, George J.; Kowalsky, Michael

    2006-05-12

    Class 1 hydrate deposits are characterized by a Hydrate-Bearing Layer (HBL) underlain by a two-phase zone involving mobile gas. Such deposits are further divided to Class 1W (involving water and hydrate in the HBL) and Class 1G (involving gas and hydrate in the HBL). In Class 2 deposits, a mobile water zone underlies the hydrate zone. Methane is the main hydrate-forming gas in natural accumulations. Using TOUGH-FX/HYDRATE to study the depressurization-induced gas production from such deposits, we determine that large volumes of gas could be readily produced at high rates for long times using conventional technology. Dissociation in Class 1W deposits proceeds in distinct stages, but is continuous in Class 1G deposits. Hydrates are shown to contribute significantly to the production rate (up to 65 percent and 75 percent in Class 1W and 1G, respectively) and to the cumulative volume of produced gas (up to 45 percent and 54 percent in Class 1W and 1G, respectively). Large volumes of hydrate-originating CH4 could be produced from Class 2 hydrates, but a relatively long lead time would be needed before gas production (which continuously increases over time) attains a substantial level. The permeability of the confining boundaries plays a significant role in gas production from Class 2 deposits. In general, long-term production is needed to realize the full potential of the very promising Class 1 and Class 2 hydrate deposits.

  12. Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

    DOE PAGES

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

    2017-02-01

    The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

  13. Geochemical and geologic factors effecting the formulation of gas hydrate: Task No. 5, Final report

    SciTech Connect

    Kvenvolden, K.A.; Claypool, G.E.

    1988-01-01

    The main objective of our work has been to determine the primary geochemical and geological factors controlling gas hydrate information and occurrence and particularly in the factors responsible for the generation and accumulation of methane in oceanic gas hydrates. In order to understand the interrelation of geochemical/geological factors controlling gas hydrate occurrence, we have undertaken a multicomponent program which has included (1) comparison of available information at sites where gas hydrates have been observed through drilling by the Deep Sea Drilling Project (DSDP) on the Blake Outer Ridge and Middle America Trench; (2) regional synthesis of information related to gas hydrate occurrences of the Middle America Trench; (3) development of a model for the occurrence of a massive gas hydrate as DSDP Site 570; (4) a global synthesis of gas hydrate occurrences; and (5) development of a predictive model for gas hydrate occurrence in oceanic sediment. The first three components of this program were treated as part of a 1985 Department of Energy Peer Review. The present report considers the last two components and presents information on the worldwide occurrence of gas hydrates with particular emphasis on the Circum-Pacific and Arctic basins. A model is developed to account for the occurrence of oceanic gas hydrates in which the source of the methane is from microbial processes. 101 refs., 17 figs., 6 tabs.

  14. Biogenic gas: Controls, habitats, and resource potential

    SciTech Connect

    Rice, D.D. )

    1993-01-01

    As much as 20 percent of the world's natural-gas resource is estimated to have been generated by the decomposition of organic matter by anaerobic microbes at low temperatures. This gas is commonly referred to as biogenic gas. Most biogenic gas was generated early in the burial history of sediments. Some biogenic gas was also generated in relatively recent geologic time and is associated with groundwater flow. The factors that favor significant generation of biogenic gas are anoxic conditions, low sulfate content, low temperature, abundant organic matter, and sufficient pore space for the microbes to thrive. Conditions beneficial for the accumulation of biogenic gas include stratigraphic or early structural traps, adequate seals, low permeability, low pressure, early dissolution of the gas, and formation of gas hydrates. Rapid sediment deposition is critical to both the generation and the accumulation of biogenic gas generated during the early stage. Biogenic gas is distinguished by its molecular and isotopic composition. The hydrocarbon fraction is generally more than 99 percent methane, and the diagnostic isotopic composition of the methane component is as follows: [delta][sup 13]C values are generally lighter than -55 parts per thousand (permil), and [delta]D values are usually in the range of -150 to -250 permil. This isotopic composition indicates that the methane generally resulted from CO[sub 2] reduction. Significant accumulations of ancient biogenic gas have been discovered in Africa, Asia, Europe, North America, and South America. These accumulations occur in Mississippian and younger rocks, at burial depths as much as 4,600 m. They are associated with a variety of rock types (carbonate, clastic, and coal), and occur in a variety of marine and nonmarine depositional settings generally characterized by rapid deposition. 111 refs., 13 figs., 3 tabs.

  15. Structure II gas hydrates found below the bottom-simulating reflector

    NASA Astrophysics Data System (ADS)

    Paganoni, M.; Cartwright, J. A.; Foschi, M.; Shipp, R. C.; Van Rensbergen, P.

    2016-06-01

    Gas hydrates are a major component in the organic carbon cycle. Their stability is controlled by temperature, pressure, water chemistry, and gas composition. The bottom-simulating reflector (BSR) is the primary seismic indicator of the base of hydrate stability in continental margins. Here we use seismic, well log, and core data from the convergent margin offshore NW Borneo to demonstrate that the BSR does not always represent the base of hydrate stability and can instead approximate the boundary between structure I hydrates above and structure II hydrates below. At this location, gas hydrate saturation below the BSR is higher than above and a process of chemical fractionation of the migrating free gas is responsible for the structure I-II transition. This research shows that in geological settings dominated by thermogenic gas migration, the hydrate stability zone may extend much deeper than suggested by the BSR.

  16. Computational phase diagrams of noble gas hydrates under pressure

    SciTech Connect

    Teeratchanan, Pattanasak Hermann, Andreas

    2015-10-21

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-I{sub h}, ice-I{sub c}, ice-II, and C{sub 0} interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C{sub 0} water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C{sub 0} hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  17. Computational phase diagrams of noble gas hydrates under pressure

    NASA Astrophysics Data System (ADS)

    Teeratchanan, Pattanasak; Hermann, Andreas

    2015-10-01

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-Ih, ice-Ic, ice-II, and C0 interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C0 water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C0 hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  18. Ocean observatory networks monitor gas hydrates systems - Updates from Cascadia

    NASA Astrophysics Data System (ADS)

    Scherwath, M.; Kelley, D. S.; Moran, K.; Philip, B. T.; Roemer, M.; Riedel, M.; Solomon, E. A.; Spence, G.; Heesemann, M.

    2015-12-01

    Seafloor observatories have been installed at the Cascadia margin with a long-term (>20 year) lifespan. These observatories consist of a variety of node locations cabled back to shore for continuous power and communication to instruments via high bandwidth internet access. Ocean Networks Canada (ONC) maintains two hydrate sites at Barkley Canyon and Clayoquot Slope off Vancouver Island, and the Ocean Observatories Initiative (OOI) Cabled Array connects to Hydrate Ridge off the Oregon coast. Together, these installations comprise a diverse suite of different experiments. For example, a seafloor crawler, operated by Jacobs University in Bremen, travels around the Barkley hydrate mounds on a daily basis and carries out a suite of measurements such as determining the rate of change of the benthic community composition. Another example is from several years of hourly sonar data showing gas bubbles rising from the seafloor near the Bullseye Vent with varying intensities, allowing statistically sound correlations with other seafloor parameters such as ground shaking, temperature and pressure variations and currents, where tidal pressure appearing as the main driver. The Southern Hydrate Ridge is now equipped with the world's first long-term seafloor mass spectrometer, co-located with a camera and lights, hydrophone, current meters, pressure sensor, autonomous dissolved oxygen and fluid samplers, and is surrounded by a seismometer array for local seismicity. In the future, long-term data will be continuously captured and made available throughout the year covering the full range of variations of the dynamic hydrate system, and expect additional experiments to be connected to the observatories from the broader research community.

  19. Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems

    NASA Astrophysics Data System (ADS)

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; Hillman, Jess I. T.; Malinverno, Alberto

    2017-02-01

    The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1-20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two-dimensional and basin-scale three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. Furthermore, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.Plain Language SummaryThis study combines one-, two-, and three-dimensional simulations to explore one potential process by which methane dissolved in water beneath the seafloor can be converted into solid methane <span class="hlt">hydrate</span>. This work specifically</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.1853R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.1853R"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> environmental monitoring program in the Ulleung Basin, East Sea of Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryu, Byong-Jae; Chun, Jong-Hwa; McLean, Scott</p> <p>2013-04-01</p> <p>As a part of the Korean National <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Program, the Korea Institute of Geoscience and Mineral <span class="hlt">Resources</span> (KIGAM) has been planned and conducted the environmental monitoring program for the <span class="hlt">gas</span> <span class="hlt">hydrate</span> production test in the Ulleung Basin, East Sea of Korea in 2014. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated <span class="hlt">gas</span> from <span class="hlt">gas</span> <span class="hlt">hydrates</span> during the production test. The KIGAM also plans to conduct the geophysical survey for determining the change of <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs and production-efficiency around the production well before and after the production test. During production test, release of <span class="hlt">gas</span> dissociated from the <span class="hlt">gas</span> <span class="hlt">hydrate</span> to the water column, seafloor deformation, changes in chemical characteristics of bottom water, changes in seafloor turbidity, etc. will be monitored by using the various monitoring instruments. The KIMOS consists of a near-field observation array and a far-field array. The near-field array is constructed with four remote sensor platforms each, and cabled to the primary node. The far-field sensor array will consists of four autonomous instrument pods. A scientific Remotely Operated Vehicle (ROV) will be used to deploy the sensor arrays, and to connect the cables to each field instrument package and a primary node. A ROV will also be tasked to collect the water and/or <span class="hlt">gas</span> samples, and to identify any <span class="hlt">gas</span> (bubble) plumes from the seafloor using a high-frequency sector scanning sonar. Power to the near-field instrument packages will be supplied by battery units located on the seafloor near the primary node. Data obtained from the instruments on the near-field array will be logged and downloaded in-situ at the primary node, and transmitted real-time to the support vessel using a ROV. These data will also be transmitted real-time to</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMOS33A1221H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMOS33A1221H"><span>The German collaborative project SUGAR Utilization of a natural treasure - Developing innovative techniques for the exploration and production of natural <span class="hlt">gas</span> from <span class="hlt">hydrate</span>-bearing sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haeckel, M.; Bialas, J.; Wallmann, K. J.</p> <p>2009-12-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> occur in nature at all active and passive continental margins as well as in permafrost regions, and vast amounts of natural <span class="hlt">gas</span> are bound in those deposits. Geologists estimate that twice as much carbon is bound in <span class="hlt">gas</span> <span class="hlt">hydrates</span> than in any other fossil fuel reservoir, such as <span class="hlt">gas</span>, oil and coal. Hence, natural <span class="hlt">gas</span> <span class="hlt">hydrates</span> represent a huge potential energy <span class="hlt">resource</span> that, in addition, could be utilized in a CO2-neutral and therefore environmentally friendly manner. However, the utilization of this natural treasure is not as easy as the conventional production of oil or natural <span class="hlt">gas</span> and calls for new and innovative techniques. In the framework of the large-scale collaborative research project SUGAR (Submarine Deposits of <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> - Exploration, Production and Transportation), we aim to produce <span class="hlt">gas</span> from methane <span class="hlt">hydrates</span> and to sequester carbon dioxide from power plants and other industrial sources as CO2 <span class="hlt">hydrates</span> in the same host sediments. Thus, the SUGAR project addresses two of the most pressing and challenging topics of our time: development of alternative energy strategies and greenhouse <span class="hlt">gas</span> mitigation techniques. The SUGAR project is funded by two federal German ministries and the German industry for an initial period of three years. In the framework of this project new technologies starting from <span class="hlt">gas</span> <span class="hlt">hydrate</span> exploration techniques over drilling technologies and innovative <span class="hlt">gas</span> production methods to CO2 storage in <span class="hlt">gas</span> <span class="hlt">hydrates</span> and <span class="hlt">gas</span> transportation technologies will be developed and tested. Beside the performance of experiments, numerical simulation studies will generate data regarding the methane production and CO2 sequestration in the natural environment. Reservoir modelling with respect to <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and development of migration pathways complete the project. This contribution will give detailed information about the planned project parts and first results with focus on the production methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020911','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020911"><span>Seismic- and well-log-inferred <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations on Richards Island</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Collett, T.S.</p> <p>1999-01-01</p> <p>The <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone is areally extensive beneath most of the Mackenzie Delta-Beaufort Sea region, with the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone more than 1000 m deep on Richards Island. In this study, <span class="hlt">gas</span> <span class="hlt">hydrate</span> has been inferred to occur in nine Richards Island exploratory wells on the basis of well-log responses calibrated to the response of the logs within the cored <span class="hlt">gas-hydrate</span>-bearing intervals of the JAPEX/JNOC/GSC Mallik 2L-38 <span class="hlt">gas</span> <span class="hlt">hydrate</span> research well. The integration of the available well-log data with more than 240 km of industry-acquired reflection seismic data have allowed us to map the occurrence of four significant <span class="hlt">gas</span> <span class="hlt">hydrate</span> and associated free-<span class="hlt">gas</span> accumulations in the Ivik-Mallik-Taglu area on Richards Island. The occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> on Richards Island is mostly restricted to the crest of large anticlinal features that cut across the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Combined seismic and well-log data analysis indicate that the known and inferred <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations on Richards Island may contain as much as 187 178106 m3 of <span class="hlt">gas</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS42A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS42A..04M"><span>Basin-Wide Temperature Constraints On <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stability In The Gulf Of Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>MacDonald, I. R.; Reagan, M. T.; Guinasso, N. L.; Garcia-Pineda, O. G.</p> <p>2012-12-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrate</span> deposits commonly occur at the seafloor-water interface on marine margins. They are especially prevalent in the Gulf of Mexico where they are associated with natural oil seeps. The stability of these deposits is potentially challenged by fluctuations in bottom water temperature, on an annual time-scale, and under the long-term influence of climate change. We mapped the locations of natural oil seeps where shallow <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits are known to occur across the entire Gulf of Mexico basin based on a comprehensive review of synthetic aperture radar (SAR) data (~200 images). We prepared a bottom water temperature map based on the archive of CTD casts from the Gulf (~6000 records). Comparing the distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits with predicted bottom water temperature, we find that a broad area of the upper slope lies above the theoretical stability horizon for structure 1 <span class="hlt">gas</span> <span class="hlt">hydrate</span>, while all sites where <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits occur are within the stability horizon for structure 2 <span class="hlt">gas</span> <span class="hlt">hydrate</span>. This is consistent with analytical results that structure 2 <span class="hlt">gas</span> <span class="hlt">hydrates</span> predominate on the upper slope (Klapp et al., 2010), where bottom water temperatures fluctuate over a 7 to 10 C range (approx. 600 m depth), while pure structure 1 <span class="hlt">hydrates</span> are found at greater depths (approx. 3000 m). Where higher hydrocarbon gases are available, formation of structure 2 <span class="hlt">gas</span> <span class="hlt">hydrate</span> should significantly increase the resistance of shallow <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits to destabilizing effects variable or increasing bottom water temperature. Klapp, S.A., Bohrmann, G., Kuhs, W.F., Murshed, M.M., Pape, T., Klein, H., Techmer, K.S., Heeschen, K.U., and Abegg, F., 2010, Microstructures of structure I and II <span class="hlt">gas</span> <span class="hlt">hydrates</span> from the Gulf of Mexico: Marine and Petroleum Geology, v. 27, p. 116-125.Bottom temperature and pressure for Gulf of Mexico <span class="hlt">gas</span> <span class="hlt">hydrate</span> outcrops and stability horizons for sI and sII <span class="hlt">hydrate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS31G..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS31G..05S"><span>The results of pressure coring in Nankai <span class="hlt">gas</span>-production test site, and plan for pressure core analysis of natural <span class="hlt">gas-hydrate</span> bearing deep-sea sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suzuki, K.; Nakatsuka, Y.; Konno, Y.; Kida, M.; Yoneda, J.; Egawa, K.; Jin, Y.; Ito, T.</p> <p>2012-12-01</p> <p> among sediments and methane <span class="hlt">hydrate</span>. Especially, data set that consists of methane <span class="hlt">hydrate</span>-saturation calculated from core analyses, lithology described from core analyses and X-ray CT images, and P-wave velocity measured by PCATS, is the most important trinity to understand the methane <span class="hlt">hydrate</span> sediments, not only for <span class="hlt">resource</span> development but also for scientific interest. We will grasp the physical properties of sediments at each depth so as to construct the models of methane <span class="hlt">hydrate</span> reservoir to simulate <span class="hlt">hydrate</span> dissociation for comparing the results of actual <span class="hlt">gas</span> production test.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020941','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020941"><span>Detailed evaluation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoir properties using JAPEX/JNOC/GSC Mallik 2L-38 <span class="hlt">gas</span> <span class="hlt">hydrate</span> research well downhole well-log displays</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Collett, T.S.</p> <p>1999-01-01</p> <p>The JAPEX/JNOC/GSC Mallik 2L-38 <span class="hlt">gas</span> <span class="hlt">hydrate</span> research well project was designed to investigate the occurrence of in situ natural <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the Mallik area of the Mackenzie Delta of Canada. Because <span class="hlt">gas</span> <span class="hlt">hydrate</span> is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the <span class="hlt">gas-hydrate</span>-bearing sediments. Downhole logging tool strings deployed in the Mallik 2L-38 well included the Schlumberger Platform Express with a high resolution laterolog, Array Induction Imager Tool, Dipole Shear Sonic Imager, and a Fullbore Formation Microlmager. The downhole log data obtained from the log- and core-inferred <span class="hlt">gas-hydrate</span>-bearing sedimentary interval (897.25-1109.5 m log depth) in the Mallik 2L-38 well is depicted in a series of well displays. Also shown are numerous reservoir parameters, including <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation and sediment porosity log traces, calculated from available downhole well-log and core data. The <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation delineated by the Mallik 2L-38 well has been determined to contain as much as 4.15109 m3 of <span class="hlt">gas</span> in the 1 km2 area surrounding the drill site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMOS21A..01Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMOS21A..01Y"><span>Introduction of the 2007-2008 JOGMEC/NRCan/Aurora Mallik <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Production Research Program, NWT, Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, K.; Dallimore, S. R.; Numasawa, M.; Yasuda, M.; Fujii, T.; Fujii, K.; Wright, J.; Nixon, F.</p> <p>2007-12-01</p> <p>Japan Oil, <span class="hlt">Gas</span> and Metals National Corporation (JOGMEC) and Natural <span class="hlt">Resource</span> Canada (NRCan) have embarked on a new research program to study the production potential of <span class="hlt">gas</span> <span class="hlt">hydrates</span>. The program is being carried out at the Mallik <span class="hlt">gas</span> <span class="hlt">hydrate</span> field in the Mackenzie Delta, a location where two previous scientific investigations have been carried in 1998 and 2002. In the 2002 program that was undertaken by seven partners from five countries, 468m3 of <span class="hlt">gas</span> flow was measured during 124 hours of thermal stimulation using hot warm fluid. Small-scale pressure drawdown tests were also carried out using Schlumberger's Modular Dynamics Tester (MDT) wireline tool, <span class="hlt">gas</span> flow was observed and the inferred formation permeabilities suggested the possible effectiveness of the simple depressurization method. While the testing undertaken in 2002 can be cited as the first well constrained <span class="hlt">gas</span> production from a <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposit, the results fell short of that required to fully calibrate reservoir simulation models or indeed establish the technical viability of long term production from <span class="hlt">gas</span> <span class="hlt">hydrates</span>. The objectives of the current JOGMEC/NRCan/Aurora Mallik production research program are to undertake longer term production testing to further constrain the scientific unknowns and to demonstrate the technical feasibility of sustained <span class="hlt">gas</span> <span class="hlt">hydrate</span> production using the depressurization method. A key priority is to accurately measure water and <span class="hlt">gas</span> production using state-of-art production technologies. The primary production test well was established during the 2007 field season with the re-entry and deepening of JAPEX/JNOC/GSC Mallik 2L-38 well, originally drilled in 1998. Production testing was carried out in April of 2007 under a relatively low drawdown pressure condition. Flow of methane <span class="hlt">gas</span> was measured from a 12m perforated interval of <span class="hlt">gas-hydrate</span>-saturated sands from 1093 to 1105m. The results establish the potential of the depressurization method and provide a basis for future</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70176408','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70176408"><span>Comparison of the physical and geotechnical properties of <span class="hlt">gas-hydrate</span>-bearing sediments from offshore India and other <span class="hlt">gas-hydrate</span>-reservoir systems</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Winters, William J.; Wilcox-Cline, R.W.; Long, P.; Dewri, S.K.; Kumar, P.; Stern, Laura A.; Kerr, Laura A.</p> <p>2014-01-01</p> <p>The sediment characteristics of <span class="hlt">hydrate</span>-bearing reservoirs profoundly affect the formation, distribution, and morphology of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The presence and type of <span class="hlt">gas</span>, porewater chemistry, fluid migration, and subbottom temperature may govern the <span class="hlt">hydrate</span> formation process, but it is the host sediment that commonly dictates final <span class="hlt">hydrate</span> habit, and whether <span class="hlt">hydrate</span> may be economically developed.In this paper, the physical properties of <span class="hlt">hydrate</span>-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other <span class="hlt">hydrate</span> reservoirs. Properties from the <span class="hlt">hydrate</span>-free Kerala-Konkan basin off the west coast of India are also presented. Coarser-grained reservoirs (permafrost-related and marine) may contain high <span class="hlt">gas-hydrate</span>-pore saturations, while finer-grained reservoirs may contain low-saturation disseminated or more complex <span class="hlt">gas-hydrates</span>, including nodules, layers, and high-angle planar and rotational veins. However, even in these fine-grained sediments, <span class="hlt">gas</span> <span class="hlt">hydrate</span> preferentially forms in coarser sediment or fractures, when present. The presence of <span class="hlt">hydrate</span> in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the Andaman Islands.Properties of individual NGHP-01 wells and regional trends are discussed in detail. However, comparison of marine and permafrost-related Arctic reservoirs provides insight into the inter-relationships and common traits between physical properties and the morphology of <span class="hlt">gas-hydrate</span> reservoirs regardless of location. Extrapolation of properties from one location to another also enhances our understanding of <span class="hlt">gas-hydrate</span> reservoir systems. Grain size and porosity effects on permeability are critical, both locally to trap <span class="hlt">gas</span> and regionally to provide fluid flow to <span class="hlt">hydrate</span> reservoirs. Index properties corroborate more advanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810738C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810738C"><span>The heat flow study of two potential <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospects off SW Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chiang, Hsiehtang</p> <p>2016-04-01</p> <p>The Formosa Ridge and Four-Way Closure off SW Taiwan have been considered potential prospects of <span class="hlt">gas</span> <span class="hlt">hydrate</span> <span class="hlt">resources</span> as the results of many geophysical and geochemistry investigations for years. Fourteen heat flow measurements located on these two prospects were completed in May, 2015. The results show that the sea floor temperature are between 2.78 and 4.01℃in Formosa Ridge and between 2.74 to 3.09℃in Four-Way Closure. The heat flow are in the range of 54 to 85 mW/m2 in Formosa Ridge and 63 to 86 mW/m2 in Four-Way Closure. It could be interpreted the moderate high heat flow and the sea floor temperature could be related to the fluid upward migration in Formosa Ridge and the erosion process in Four-Way Closure while examining the seismic profiles. The BGHS (Base of <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stability) are in the range of 166 to 284 meters in Formosa Ridge and 108 to 246 meters in Four-Way Closure. All the measurements of BGHS are shallower than that the average, 320 meters acquired off SW Taiwan. The heat flow data lead a chance to implement the drilling project in the future while considering the estimations of the reserves of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> and the evaluations of the fluid migration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70004248','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70004248"><span>Multicomponent seismic methods for characterizing <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrences and systems in deep-water Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Haines, Seth S.; Lee, Myung W.; Collett, Timothy S.; Hardage, Bob A.</p> <p>2011-01-01</p> <p>In-situ characterization and quantification of natural <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrences remain critical research directions, whether for energy <span class="hlt">resource</span>, drilling hazard, or climate-related studies. Marine multicomponent seismic data provide the full seismic wavefield including partial redundancy, and provide a promising set of approaches for <span class="hlt">gas</span> <span class="hlt">hydrate</span> characterization. Numerous authors have demonstrated the possibilities of multicomponent data at study sites around the world. We expand on this work by investigating the utility of very densely spaced (10’s of meters) multicomponent receivers (ocean-bottom cables, OBC, or ocean-bottom seismometers, OBS) for <span class="hlt">gas</span> <span class="hlt">hydrate</span> studies in the Gulf of Mexico and elsewhere. Advanced processing techniques provide high-resolution compressional-wave (PP) and converted shearwave (PS) reflection images of shallow stratigraphy, as well as P-wave and S-wave velocity estimates at each receiver position. Reflection impedance estimates can help constrain velocity and density, and thus <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation. Further constraint on velocity can be determined through identification of the critical angle and associated phase reversal in both PP and PS wideangle data. We demonstrate these concepts with examples from OBC data from the northeast Green Canyon area and numerically simulated OBS data that are based on properties of known <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrences in the southeast (deeper water) Green Canyon area. These multicomponent data capabilities can provide a wealth of characterization and quantification information that is difficult to obtain with other geophysical methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B13B0607K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B13B0607K"><span>Importance of Pore Size Distribution of Fine-grained Sediments on <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Equilibrium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kwon, T. H.; Kim, H. S.; Cho, G. C.; Park, T. H.</p> <p>2015-12-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> have been considered as a new source of natural gases. For the <span class="hlt">gas</span> <span class="hlt">hydrate</span> production, the <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoir should be depressurized below the equilibrium pressure of <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Therefore, it is important to predict the equilibrium of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in the reservoir conditions because it can be affected by the pore size of the host sediments due to the capillary effect. In this study, <span class="hlt">gas</span> <span class="hlt">hydrates</span> were synthesized in fine-grained sediment samples including a pure silt sample and a natural clayey silt sample cored from a <span class="hlt">hydrate</span> occurrence region in Ulleung Basin, East Sea, offshore Korea. Pore size distributions of the samples were obtained by the nitrogen adsorption and desorption test and the mercury intrusion porosimetry. The equilibrium curve of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in the fine-grained sediments were found to be significantly influenced by the clay fraction and the corresponding small pores (>50 nm in diameter). For the clayey silt sample, the equilibrium pressure was higher by ~1.4 MPa than the bulk equilibrium pressure. In most cases of oceanic <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs, sandy layers are found interbedded with fine-grained sediment layers while <span class="hlt">gas</span> <span class="hlt">hydrates</span> are intensively accumulated in the sandy layers. Our experiment results reveal the inhibition effect of fine-grained sediments against <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation, in which greater driving forces (e.g., higher pressure or lower temperature) are required during natural <span class="hlt">gas</span> migration. Therefore, <span class="hlt">gas</span> <span class="hlt">hydrate</span> distribution in interbedded layers of sandy and fine-grained sediments can be explained by such capillary effect induced by the pore size distribution of host sediments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/893471','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/893471"><span>Unconventional Oil and <span class="hlt">Gas</span> <span class="hlt">Resources</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>2006-09-15</p> <p>World oil use is projected to grow to 98 million b/d in 2015 and 118 million b/d in 2030. Total world natural <span class="hlt">gas</span> consumption is projected to rise to 134 Tcf in 2015 and 182 Tcf in 2030. In an era of declining production and increasing demand, economically producing oil and <span class="hlt">gas</span> from unconventional sources is a key challenge to maintaining global economic growth. Some unconventional hydrocarbon sources are already being developed, including <span class="hlt">gas</span> shales, tight <span class="hlt">gas</span> sands, heavy oil, oil sands, and coal bed methane. Roughly 20 years ago, <span class="hlt">gas</span> production from tight sands, shales, and coals was considered uneconomic. Today, these <span class="hlt">resources</span> provide 25% of the U.S. <span class="hlt">gas</span> supply and that number is likely to increase. Venezuela has over 300 billion barrels of unproven extra-heavy oil reserves which would give it the largest reserves of any country in the world. It is currently producing over 550,000 b/d of heavy oil. Unconventional oil is also being produced in Canada from the Athabasca oil sands. 1.6 trillion barrels of oil are locked in the sands of which 175 billion barrels are proven reserves that can be recovered using current technology. Production from 29 companies now operating there exceeds 1 million barrels per day. The report provides an overview of continuous petroleum sources and gives a concise overview of the current status of varying types of unconventional oil and <span class="hlt">gas</span> <span class="hlt">resources</span>. Topics covered in the report include: an overview of the history of Oil and Natural <span class="hlt">Gas</span>; an analysis of the Oil and Natural <span class="hlt">Gas</span> industries, including current and future production, consumption, and reserves; a detailed description of the different types of unconventional oil and <span class="hlt">gas</span> <span class="hlt">resources</span>; an analysis of the key business factors that are driving the increased interest in unconventional <span class="hlt">resources</span>; an analysis of the barriers that are hindering the development of unconventional <span class="hlt">resources</span>; profiles of key producing regions; and, profiles of key unconventional oil and <span class="hlt">gas</span> producers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pet.hw.ac.uk/icgh7/authors3.html#L','USGSPUBS'); return false;" href="http://www.pet.hw.ac.uk/icgh7/authors3.html#L"><span>A petroleum system model for <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits in northern Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lorenson, T.D.; Collett, Timothy S.; Wong, Florence L.</p> <p>2011-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrate</span> deposits are common on the North Slope of Alaska around Prudhoe Bay, however the extent of these deposits is unknown outside of this area. As part of a United States Geological Survey (USGS) and the Bureau of Land Management (BLM) <span class="hlt">gas</span> <span class="hlt">hydrate</span> research collaboration, well cutting and mud <span class="hlt">gas</span> samples have been collected and analyzed from mainly industry-drilled wells on the Alaska North Slope for the purpose of prospecting for <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits. On the Alaska North Slope, <span class="hlt">gas</span> <span class="hlt">hydrates</span> are now recognized as an element within a petroleum systems approach or TPS (Total Petroleum System). Since 1979, 35 wells have been samples from as far west as Wainwright to Prudhoe Bay in the east. Geochemical studies of known <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrences on the North Slope have shown a link between <span class="hlt">gas</span> <span class="hlt">hydrate</span> and more deeply buried conventional oil and <span class="hlt">gas</span> deposits. Hydrocarbon gases migrate from depth and charge the reservoir rock within the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. It is likely gases migrated into conventional traps as free <span class="hlt">gas</span>, and were later converted to <span class="hlt">gas</span> <span class="hlt">hydrate</span> in response to climate cooling concurrent with permafrost formation. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> is known to occur in one of the sampled wells, likely present in 22 others based <span class="hlt">gas</span> geochemistry and inferred by equivocal <span class="hlt">gas</span> geochemistry in 11 wells, and absent in one well. <span class="hlt">Gas</span> migration routes are common in the North Slope and include faults and widespread, continuous, shallowly dipping permeable sand sections that are potentially in communication with deeper oil and <span class="hlt">gas</span> sources. The application of this model with the geochemical evidence suggests that <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits may be widespread across the North Slope of Alaska.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H51L1368B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H51L1368B"><span>Methane <span class="hlt">hydrate</span> behavior when exposed to a 23% carbon dioxide 77% nitrogen <span class="hlt">gas</span> under conditions similar to the ConocoPhillips 2012 Ignik Sikumi <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Field Trial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borglin, S. E.; Kneafsey, T. J.; Nakagawa, S.</p> <p>2013-12-01</p> <p>In-situ replacement of methane <span class="hlt">hydrate</span> by carbon dioxide <span class="hlt">hydrate</span> is considered to be a promising technique for producing natural <span class="hlt">gas</span>, while simultaneously sequestering greenhouse <span class="hlt">gas</span> in deep geological formations. For effective application of this technique in the field, kinetic models of <span class="hlt">gas</span> exchange rates in <span class="hlt">hydrate</span> under a variety of environmental conditions need to be established, and the impact of <span class="hlt">hydrate</span> substitution on geophysical (seismic) properties has to be quantified in order to optimize monitoring techniques. We performed a series of laboratory tests in which we monitored changes in methane <span class="hlt">hydrate</span>-bearing samples while a nitrogen/carbon dioxide <span class="hlt">gas</span> mixture was flowed through. These experiments were conducted to gain insights into data obtained from a field test in which the same mixture of carbon dioxide and nitrogen was injected into a methane <span class="hlt">hydrate</span>-bearing unit beneath the north slope of the Brooks Range in northern Alaska (ConocoPhillips 2012 Ignik Sikumi <span class="hlt">gas</span> <span class="hlt">hydrate</span> field trial). We have measured the kinetic <span class="hlt">gas</span> exchange rate for a range of <span class="hlt">hydrate</span> saturations and different test configurations, to provide an estimate for comparison to numerical model predictions. In our tests, the exchange rate decreased over time during the tests as methane was depleted from the system. Following the elution of residual gaseous methane, the exchange rate ranged from 3.8×10-7 moles methane/(mole water*s) to 5×10-8 moles methane/(mole water*s) (Note that in these rates, the moles of water refers to water originally held in the <span class="hlt">hydrate</span>.). In addition to the <span class="hlt">gas</span> exchange rate, we also monitored changes in permeability occurring due to the <span class="hlt">gas</span> substitution. Further, we determined the seismic P and S wave velocities and attenuations using our Split Hopkinson Resonant Bar apparatus (e.g. Nakagawa, 2012, Rev. Sci. Instr.). In addition to providing geophysical signatures, changes in the seismic properties can also be related to changes in the mechanical strength of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5640235','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5640235"><span>Oil-based drilling mud as a <span class="hlt">gas-hydrates</span> inhibitor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grigg, R.B.; Lynes, G.L. )</p> <p>1992-03-01</p> <p><span class="hlt">Gas-hydrates</span> formation must be considered when petroleum reservoirs are developed in arctic regions and deepwater environments. This paper demonstrates that <span class="hlt">gas</span> <span class="hlt">hydrates</span> can form in oil-based muds, but that two major components - oil and dissolved solids in the aqueous phase - significantly inhibit this formation. This work identifies two major components in oil-based drilling mud that affect <span class="hlt">gas-hydrates</span> formation. The temperature and extent of <span class="hlt">gas-hydrates</span> formation both can be inhibited significantly, but not necessarily prevented, in oil-based drilling muds. A system that contained 20-vol % water and has an oil-continuous phase inhibited <span class="hlt">gas-hydrates</span> formation 5 to 10{degrees} F. Dissolved solids in a 19.22-wt% calcium chloride (CaCl{sub 2}) brine inhibited <span class="hlt">gas-hydrates</span> formation 20 to 25{degrees} F and significantly reduced the extent of formation. <span class="hlt">Gas-hydrates</span> formation in an oil-based drilling mud, prepared with 20-vol%, 19.22-wt% brine, was inhibited more than 30{degrees} F over the pressure range studied, 500 to 4,500 psig. In most cases, oil-based mud can be prepared with sufficient concentrations of dissolved solids to prevent <span class="hlt">gas-hydrates</span> formation under downhole conditions. Mud samples should be tested to determine the temperature of <span class="hlt">gas-hydrates</span> formation before field use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RJPCA..89.2178Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RJPCA..89.2178Z"><span>Equilibrium conditions and the region of metastable states of Freon-12 <span class="hlt">gas</span> <span class="hlt">hydrate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zavodovsky, A. G.; Madygulov, M. Sh.; Reshetnikov, A. M.</p> <p>2015-12-01</p> <p>The results from DTA experiments to determine the thermodynamic parameters of equilibrium of Freon-12 <span class="hlt">gas</span> <span class="hlt">hydrate</span> with water (super cooled water), <span class="hlt">gas</span>, and ice are analyzed. Empirical relations are obtained for determining the positions of the boundaries in the region of metastable states of Freon-12 <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the P-T phase diagram. The enthalpies of dissociation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> to water and ice are calculated. The size of pores in Freon-12 <span class="hlt">hydrate</span> formed from granules of ground ice is estimated from the magnitude of the shift in the quadrupole point at temperatures below 273 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025450','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025450"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> volume estimations on the South Shetland continental margin, Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jin, Y.K.; Lee, M.W.; Kim, Y.; Nam, S.H.; Kim, K.J.</p> <p>2003-01-01</p> <p>Multi-channel seismic data acquired on the South Shetland margin, northern Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of <span class="hlt">gas</span> <span class="hlt">hydrates</span>. In order to estimate the volume of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the area, interval velocities were determined using a 1-D velocity inversion method and porosities were deduced from their relationship with sub-bottom depth for terrigenous sediments. Because data such as well logs are not available, we made two baseline models for the velocities and porosities of non-<span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sediments in the area, considering the velocity jump observed at the shallow sub-bottom depth due to joint contributions of <span class="hlt">gas</span> <span class="hlt">hydrate</span> and a shallow unconformity. The difference between the results of the two models is not significant. The parameters used to estimate the total volume of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of <span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sediments, and 6.3% of the average volume <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentration (based on the second baseline model). Assuming that <span class="hlt">gas</span> <span class="hlt">hydrates</span> exist only where BSRs are observed, the total volume of <span class="hlt">gas</span> <span class="hlt">hydrates</span> along the seismic profiles in the area is about 4.8 ?? 1010 m3 (7.7 ?? 1012 m3 volume of methane at standard temperature and pressure).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003E%26PSL.209..291B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003E%26PSL.209..291B"><span>Geological controls on the Storegga <span class="hlt">gas-hydrate</span> system of the mid-Norwegian continental margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bünz, Stefan; Mienert, Jürgen; Berndt, Christian</p> <p>2003-04-01</p> <p>The geologic setting of the formerly glaciated mid-Norwegian continental margin exerts specific controls on the formation of a bottom-simulating reflector (BSR) and the inferred distribution of <span class="hlt">gas</span> <span class="hlt">hydrates</span>. On the continental slope the lithology of glacigenic debris flow deposits and pre-glacial basin deposits of the Kai Formation prevent <span class="hlt">gas-hydrate</span> formation, because of reduced pore size, reduced water content and fine-grained sediment composition. Towards the continental shelf, the shoaling and pinch-out of the <span class="hlt">gas-hydrate</span> stability zone terminates the area of <span class="hlt">gas-hydrate</span> growth. These geological controls confine the occurrence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> and ensuing formation of a BSR to a small zone along the northern flank of the Storegga submarine slide and the slide area itself. A BSR inside the slide area indicates a dynamically adjusting <span class="hlt">gas-hydrate</span> system to post-slide pressure-temperature equilibrium conditions. These observations, together with widespread evidence for fluid flow and deep-seated hydrocarbon reservoirs, suggest that the formation of BSR and <span class="hlt">gas</span> <span class="hlt">hydrates</span> on the mid-Norwegian continental margin is dominated by an advection of <span class="hlt">gas</span> from the strata distinctly beneath the <span class="hlt">gas-hydrate</span> stability zone. Fluids migrate upward within the Naust Formation and are deflected laterally by <span class="hlt">hydrated</span> sediments and less permeable layers. Gases continually accumulate at the top of the slope, where overpressure eventually results in the formation of blow-out pipes and consequent pockmark development on the seabed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..33.3304W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..33.3304W"><span>First results from a marine controlled-source electromagnetic survey to detect <span class="hlt">gas</span> <span class="hlt">hydrates</span> offshore Oregon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weitemeyer, K. A.; Constable, S. C.; Key, K. W.; Behrens, J. P.</p> <p>2006-02-01</p> <p>Submarine <span class="hlt">gas</span> <span class="hlt">hydrate</span> is a hazard to drilling, a potential hydrocarbon <span class="hlt">resource</span>, and has been implicated as a factor in both submarine slope stability and climate change. Bulk in situ electrical resistivities evaluated from electromagnetic surveys have the potential to provide an estimate of the total <span class="hlt">hydrate</span> volume fraction more directly than by using seismic and well log data. We conducted a marine controlled-source electromagnetic sounding at <span class="hlt">Hydrate</span> Ridge, Oregon, USA, in August, 2004. Electromagnetic fields transmitted by a deep-towed horizontal electric dipole source were measured by a linear array of 25 seafloor electromagnetic receivers, positioned 600 m apart to produce a dense coverage in the recorded electric field data. Results are presented in simple form by apparent resistivity pseudosections, which produce an approximate image of lateral resistivity variations across the study region. Resistivity values are consistent with those from well logs collected in the area and pseudosection features are correlated with seismic reflectors. Archie's Law, based on pseudosection apparent resistivities, predicts volumetric <span class="hlt">hydrate</span> concentrations vary from 0-30% across the ridge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMOS23A1059H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMOS23A1059H"><span><span class="hlt">Gas</span> <span class="hlt">Hydrates</span> on the Norway-Barents Sea-Svalbard margin(GANS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haflidason, H.; Mienert, J.; Kvamme, B.; Barth, T.; Knies, J.; Kvalstad, T.; Hoiland, S.; Planke, S.; Andersen, E. S.; Riis, F.; Hjelstuen, B. O.; Bunz, S.; Chand, S.</p> <p>2007-12-01</p> <p>The main objective of this Norwegian national initiative is to quantify <span class="hlt">gas</span> accumulations in the form of <span class="hlt">hydrates</span> in sediments on the Norway-Barents Sea-Svalbard margins, including an assessment of their dynamics and impacts on the seabed to provide knowledge; vital for a safe exploitation in oil and <span class="hlt">gas</span> production. This overall objective is an initiative by five research institutions and the Norwegian Deepwater Programme, SEABED III (consortium of nine petroleum companies), to make a coordinated effort on a national level to achieve the main objective to make a coordinated effort on a national level to achieve the main objective by the following sub-goals: a) Geophysical characterisation of <span class="hlt">gas</span> <span class="hlt">hydrates</span>, b) Geological and geochemical setting of <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs and seeps, c) <span class="hlt">Gas</span> <span class="hlt">hydrate</span> dissociation and its effects on geomechanical properties, d) Theoretical and experimental evaluation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> dynamics. Three contrasting target areas are of particular interest for field studies and experiments: (1) the mid-Norwegian margin at Nyegga, a national laboratory for <span class="hlt">gas</span> <span class="hlt">hydrate</span> research, (2) the Svalbard margin frontier area; important for understanding the geological controls on <span class="hlt">gas</span> <span class="hlt">hydrates</span> and fluids, and (3) the Barents Sea, a prolific area with possible occurrence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> and clear evidence for active cold seeps. Our initiative allows for the establishment of an acknowledged Norwegian academia-industry network on <span class="hlt">gas</span> <span class="hlt">hydrates</span> where education of a new generation of interdisciplinarily trained scientists will be a central task. Our aims are to be achieved by integrating detailed geophysical studies of zones of <span class="hlt">gas</span> <span class="hlt">hydrates</span> and associated free <span class="hlt">gas</span> in cooperation with geotechnical laboratory experiments, theoretical and experimental <span class="hlt">gas</span> <span class="hlt">hydrate</span> dynamic studies, geological studies, and geochemical studies of the fluids. The project is financed through the Norwegian Research Council - Petromaks (40 percent) and the SEABED III industry consortium (60</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.1719B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.1719B"><span>Global Assessment of Methane <span class="hlt">Gas</span> <span class="hlt">Hydrates</span>: Outreach for the public and policy makers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beaudoin, Yannick</p> <p>2010-05-01</p> <p>The United Nations Environment Programme (UNEP), via its official collaborating center in Norway, GRID-Arendal, is in the process of implementing a Global Assessment of Methane <span class="hlt">Gas</span> <span class="hlt">Hydrates</span>. Global reservoirs of methane <span class="hlt">gas</span> have long been the topic of scientific discussion both in the realm of environmental issues such as natural forces of climate change and as a potential energy <span class="hlt">resource</span> for economic development. Of particular interest are the volumes of methane locked away in frozen molecules known as clathrates or <span class="hlt">hydrates</span>. Our rapidly evolving scientific knowledge and technological development related to methane <span class="hlt">hydrates</span> makes these formations increasingly prospective to economic development. In addition, global demand for energy continues, and will continue to outpace supply for the foreseeable future, resulting in pressure to expand development activities, with associated concerns about environmental and social impacts. Understanding the intricate links between methane <span class="hlt">hydrates</span> and 1) natural and anthropogenic contributions to climate change, 2) their role in the carbon cycle (e.g. ocean chemistry) and 3) the environmental and socio-economic impacts of extraction, are key factors in making good decisions that promote sustainable development. As policy makers, environmental organizations and private sector interests seek to forward their respective agendas which tend to be weighted towards applied research, there is a clear and imminent need for a an authoritative source of accessible information on various topics related to methane <span class="hlt">gas</span> <span class="hlt">hydrates</span>. The 2008 United Nations Environment Programme Annual Report highlighted methane from the Arctic as an emerging challenge with respect to climate change and other environmental issues. Building upon this foundation, UNEP/GRID-Arendal, in conjunction with experts from national <span class="hlt">hydrates</span> research groups from Canada, the US, Japan, Germany, Norway, India and Korea, aims to provide a multi-thematic overview of the key</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70131478','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70131478"><span>Permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrate</span>: is it really approximately 1% of the global system?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ruppel, Carolyn</p> <p>2015-01-01</p> <p>Permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrates</span> are often assumed to contain ∼1 % of the global <span class="hlt">gas</span>-in-place in <span class="hlt">gas</span> <span class="hlt">hydrates</span> based on a study26 published over three decades ago. As knowledge of permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrates</span> has grown, it has become clear that many permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrates</span> are inextricably linked to an associated conventional petroleum system, and that their formation history (trapping of migrated <span class="hlt">gas</span> in situ during Pleistocene cooling) is consistent with having been sourced at least partially in nearby thermogenic <span class="hlt">gas</span> deposits. Using modern data sets that constrain the distribution of continuous permafrost onshore5 and subsea permafrost on circum-Arctic Ocean continental shelves offshore and that estimate undiscovered conventional <span class="hlt">gas</span> within arctic assessment units,16 the done here reveals where permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrates</span> are most likely to occur, concluding that Arctic Alaska and the West Siberian Basin are the best prospects. A conservative estimate is that 20 Gt C (2.7·1013 kg CH4) may be sequestered in permafrost-associated <span class="hlt">gas</span> <span class="hlt">hydrates</span> if methane were the only <span class="hlt">hydrate</span>-former. This value is slightly more than 1 % of modern estimates (corresponding to 1600 Gt C to 1800 Gt C2,22) for global <span class="hlt">gas</span>-in-place in methane <span class="hlt">hydrates</span> and about double the absolute estimate (11.2 Gt C) made in 1981.26</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6278969','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6278969"><span>Sonic and resistivity measurements on Berea sandstone containing tetrahydrofuran <span class="hlt">hydrates</span>: a possible analogue to natural-<span class="hlt">gas-hydrate</span> deposits. [Tetrahydrofuran <span class="hlt">hydrates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pearson, C.; Murphy, J.; Halleck, P.; Hermes, R.; Mathews, M.</p> <p>1983-01-01</p> <p>Deposits of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span> exist in arctic sedimentary basins and in marine sediments on continental slopes and rises. However, the physical properties of such sediments are largely unknown. In this paper, we report laboratory sonic and resistivity measurements on Berea sandstone cores saturated with a stoichiometric mixture of tetrahydrofuran (THF) and water. We used THF as the guest species rather than methane or propane <span class="hlt">gas</span> because THF can be mixed with water to form a solution containing proportions of the proper stoichiometric THF and water. Because neither methane nor propane is soluble in water, mixing the guest species with water sufficiently to form solid <span class="hlt">hydrate</span> is difficult. Because THF solutions form <span class="hlt">hydrates</span> readily at atmospheric pressure it is an excellent experimental analogue to natural <span class="hlt">gas</span> <span class="hlt">hydrates</span>. <span class="hlt">Hydrate</span> formation increased the sonic P-wave velocities from a room temperature value of 2.5 km/s to 4.5 km/s at -5/sup 0/C when the pores were nearly filled with <span class="hlt">hydrates</span>. Lowering the temperature below -5/sup 0/C did not appreciably change the velocity however. In contrast, the electrical resistivity increases nearly two orders of magnitude upon <span class="hlt">hydrate</span> formation and continues to increase more slowly as the temperature is further decreased. In all cases the resistivities are nearly frequency independent to 30 kHz and the loss tangents are high, always greater than 5. The dielectric loss shows a linear decrease with frequency suggesting that ionic conduction through a brine phase dominates at all frequencies, even when the pores are nearly filled with <span class="hlt">hydrates</span>. We find that the resistivities are strongly a function of the dissolved salt content of the pore water. Pore water salinity also influences the sonic velocity, but this effect is much smaller and only important near the <span class="hlt">hydrate</span> formation temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3741619','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3741619"><span>Hydrophobic amino acids as a new class of kinetic inhibitors for <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sa, Jeong-Hoon; Kwak, Gye-Hoon; Lee, Bo Ram; Park, Da-Hye; Han, Kunwoo; Lee, Kun-Hong</p> <p>2013-01-01</p> <p>As the foundation of energy industry moves towards <span class="hlt">gas</span>, flow assurance technology preventing pipelines from <span class="hlt">hydrate</span> blockages becomes increasingly significant. However, the principle of <span class="hlt">hydrate</span> inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic <span class="hlt">hydrate</span> inhibitors (KHIs), and investigated <span class="hlt">hydrate</span> inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in <span class="hlt">hydrate</span> inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of <span class="hlt">hydrate</span> formation for natural <span class="hlt">gas</span> exploitation and the utilization of <span class="hlt">hydrates</span> as next-generation <span class="hlt">gas</span> capture media. PMID:23938301</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70035751','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70035751"><span>Pre- and post-drill comparison of the Mount Elbert <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospect, Alaska North Slope</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lee, M.W.; Agena, W.F.; Collett, T.S.; Inks, T.L.</p> <p>2011-01-01</p> <p>In 2006, the United States Geological Survey (USGS) completed a detailed analysis and interpretation of available 2-D and 3-D seismic data, along with seismic modeling and correlation with specially processed downhole well log data for identifying potential <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations on the North Slope of Alaska. A methodology was developed for identifying sub-permafrost <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospects within the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone in the Milne Point area. The study revealed a total of 14 <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospects in this area.In order to validate the <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospecting protocol of the USGS and to acquire critical reservoir data needed to develop a longer-term production testing program, a stratigraphic test well was drilled at the Mount Elbert prospect in the Milne Point area in early 2007. The drilling confirmed the presence of two prominent <span class="hlt">gas-hydrate</span>-bearing units in the Mount Elbert prospect, and high quality well logs and core data were acquired. The post-drill results indicate pre-drill predictions of the reservoir thickness and the <span class="hlt">gas-hydrate</span> saturations based on seismic and existing well data were 90% accurate for the upper unit (<span class="hlt">hydrate</span> unit D) and 70% accurate for the lower unit (<span class="hlt">hydrate</span> unit C), confirming the validity of the USGS approach to <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospecting. The Mount Elbert prospect is the first <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation on the North Slope of Alaska identified primarily on the basis of seismic attribute analysis and specially processed downhole log data. Post-drill well log data enabled a better constraint of the elastic model and the development of an improved approach to the <span class="hlt">gas</span> <span class="hlt">hydrate</span> prospecting using seismic attributes. ?? 2009.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018724','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018724"><span>A review of the geochemistry of methane in natural <span class="hlt">gas</span> <span class="hlt">hydrate</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kvenvolden, K.A.</p> <p>1995-01-01</p> <p>The largest accumulations on Earth of natural <span class="hlt">gas</span> are in the form of <span class="hlt">gas</span> <span class="hlt">hydrate</span>, found mainly offshore in outer continental margin sediment and, to a lesser extent, in polar regions commonly associated with permafrost. Measurements of hydrocarbon <span class="hlt">gas</span> compositions and of carbon-isotopic compositions of methane from natural <span class="hlt">gas</span> <span class="hlt">hydrate</span> samples, collected in subaquatic settings from around the world, suggest that methane guest molecules in the water clathrate structures are mainly derived by the microbial reduction of CO2 from sedimentary organic matter. In only 2 regions, the Gulf of Mexico and the Caspian Sea, has mainly thermogenic methane been found in <span class="hlt">gas</span> <span class="hlt">hydrate</span>. At a few locations, where the <span class="hlt">gas</span> <span class="hlt">hydrate</span> contains a mixture of microbial and thermal methane, microbial methane is always dominant. Continental <span class="hlt">gas</span> <span class="hlt">hydrate</span>, identified in Alaska and Russia, also has hydrocarbon gases composed of >99% methane, with carbon-isotopic compositions ranging from -41 to -49???. -from Author</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710310M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710310M"><span><span class="hlt">Gas</span> and <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Potential Offshore Amasra,Bartin and Zonguldak and Possible Agent for Multiple BSR Occurrence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mert Küçük, Hilmi; Dondurur, Derman; Özel, Özkan; Sınayuç, Çağlar; Merey, Şükrü; Parlaktuna, Mahmut; Çifçi, Günay</p> <p>2015-04-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span>, shallow gases and mud volcanoes have been studied intensively in the Black Sea in recent years. Researches have shown that the Black Sea region has an important potential about hydrocarbon. BSR reflections in the seismic sections and seabed sampling studies also have proven the formations of <span class="hlt">hydrates</span> clearly. In this respect, total of 2400 km multichannel seismic reflection, chirp and multibeam bathymetry data were collected along shelf to abyssal plain in 2010 and 2012 offshore Amasra, Bartın, Zonguldak-Kozlu in the central Black Sea.. Collected data represent BSRs, bright spots and transparent zones. It has been clearly observed that possible <span class="hlt">gas</span> chimneys cross the base of <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zones as a result of possible weak zones in the <span class="hlt">gas</span> <span class="hlt">hydrate</span> bearing sediments. Seabed samples were collected closely to possible <span class="hlt">gas</span> chimneys due to shallow <span class="hlt">gas</span> anomalies in the data. Head space <span class="hlt">gas</span> cromatography was applied to seabed samples to observe <span class="hlt">gas</span> composition and the <span class="hlt">gas</span> cromatography results represented hydrocarbon gases such as Methane, Ethane, Propane, i-Butane, n-Butane, i-Pentane, n-Pentane and Hexane. Thermogenic <span class="hlt">gas</span> production by Turkish Petroleum Corp. from Akçakoca-1 and Ayazlı-1 well is just located at the southwest of the study area and the observations of the study area point out there is also thermogenic <span class="hlt">gas</span> potential at the eastern side of the Akçakoca. In addition, multiple-BSRs were observed in the study area and it is thought the key point of the multiple-BSRs are different <span class="hlt">gas</span> compositions. This suggests that <span class="hlt">hydrate</span> formations can be formed by <span class="hlt">gas</span> mixtures. Changing of the thermobaric conditions can trigger dissociation of the <span class="hlt">gas</span> <span class="hlt">hydrates</span> in the marine sediments due to sedimentary load and changing of the water temperature around seabed. Our <span class="hlt">gas</span> <span class="hlt">hydrate</span> modelling study suggest that <span class="hlt">gas</span> <span class="hlt">hydrates</span> are behaving while their dissociation process if the <span class="hlt">gas</span> <span class="hlt">hydrates</span> are generated by <span class="hlt">gas</span> mixture. Monitoring of our <span class="hlt">gas</span> <span class="hlt">hydrate</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS21A1108M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS21A1108M"><span>Production Characteristics of Oceanic Natural <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Reservoirs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Max, M. D.; Johnson, A. H.</p> <p>2014-12-01</p> <p>Oceanic natural <span class="hlt">gas</span> <span class="hlt">hydrate</span> (NGH) accumulations form when natural <span class="hlt">gas</span> is trapped thermodynamically within the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone (GHSZ), which extends downward from the seafloor in open ocean depths greater than about 500 metres. As water depths increase, the thickness of the GHSZ thickens, but economic NGH deposits probably occur no deeper than 1 km below the seafloor. Natural <span class="hlt">gas</span> (mostly methane) appears to emanate mostly from deeper sources and migrates into the GHSZ. The natural <span class="hlt">gas</span> crystallizes as NGH when the pressure - temperature conditions within the GHSZ are reached and when the chemical condition of dissolved <span class="hlt">gas</span> concentration in pore water is high enough to favor crystallization. Although NGH can form in both primary and secondary porosity, the principal economic target appears to be turbidite sands on deep continental margins. Because these are very similar to the hosts of more deeply buried conventional <span class="hlt">gas</span> and oil deposits, industry knows how to explore for them. Recent improvements in a seismic geotechnical approach to NGH identification and valuation have been confirmed by drilling in the northern Gulf of Mexico and allow for widespread exploration for NGH deposits to begin. NGH concentrations occur in the same semi-consolidated sediments in GHSZs worldwide. This provides for a narrow exploration window with low acoustic attenuation. These sediments present the same range of relatively easy drilling conditions and formation pressures that are only slightly greater than at the seafloor and are essentially equalized by water in wellbores. Expensive conventional drilling equipment is not required. NGH is the only hydrocarbon that is stable at its formation pressures and incapable of converting to <span class="hlt">gas</span> without artificial stimulation. We suggest that specialized, NGH-specific drilling capability will offer opportunities for much less expensive drilling, more complex wellbore layouts that improve reservoir connectivity and in which <span class="hlt">gas</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS43B1815E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS43B1815E"><span>CO2 + N2O mixture <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation kinetics and effect of soil minerals on mixture-<span class="hlt">gas</span> <span class="hlt">hydrate</span> formation process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Enkh-Amgalan, T.; Kyung, D.; Lee, W.</p> <p>2012-12-01</p> <p>CO2 mitigation is one of the most pressing global scientific topics in last 30 years. Nitrous oxide (N2O) is one of the main greenhouse gases (GHGs) defined by the Kyoto Protocol and its global warming potential (GWP) of one metric ton is equivalent to 310 metric tons of CO2. They have similar physical and chemical properties and therefore, mixture-<span class="hlt">gas</span> (50% CO2 + 50% N2O) <span class="hlt">hydrate</span> formation process was studied experimentally and computationally. There were no significant research to reduce N20 <span class="hlt">gas</span> and we tried to make <span class="hlt">hydrate</span> to mitigate N20 and CO2 in same time. Mixture <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation periods were approximately two times faster than pure N2O <span class="hlt">hydrate</span> formation kinetic in general. The fastest induction time of mixture-<span class="hlt">gas</span> <span class="hlt">hydrate</span> formation observed in Illite and Quartz among various soil mineral suspensions. It was also observed that <span class="hlt">hydrate</span> formation kinetic was faster with clay mineral suspensions such as Nontronite, Sphalerite and Montmorillonite. Temperature and pressure change were not significant on <span class="hlt">hydrate</span> formation kinetic; however, induction time can be significantly affected by various chemical species forming under the different suspension pHs. The distribution of chemical species in each mineral suspension was estimated by a chemical equilibrium model, PHREEQC, and used for the identification of <span class="hlt">hydrate</span> formation characteristics in the suspensions. With the experimental limitations, a study on the molecular scale modeling has a great importance for the prediction of phase behavior of the <span class="hlt">gas</span> <span class="hlt">hydrates</span>. We have also performed molecular dynamics computer simulations on N2O and CO2 <span class="hlt">hydrate</span> structures to estimate the residual free energy of two-phase (<span class="hlt">hydrate</span> cage and guest molecule) at three different temperature ranges of 260K, 273K, and 280K. The calculation result implies that N2O <span class="hlt">hydrates</span> are thermodynamically stable at real-world <span class="hlt">gas</span> <span class="hlt">hydrate</span> existing condition within given temperature and pressure. This phenomenon proves that mixture-<span class="hlt">gas</span> could be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70127361','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70127361"><span>GHASTLI-determining physical properties of sediment containing natural and laboratory-formed <span class="hlt">gas</span> <span class="hlt">hydrate</span>: Chapter 24</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Winters, William J.; Dillon, William P.; Pecher, Ingo A.; Mason, David H.; Max, Michael D.</p> <p>2003-01-01</p> <p><span class="hlt">Gas-hydrate</span> samples have been recovered at about 16 areas worldwide (Booth et al., 1996). However, <span class="hlt">gas</span> <span class="hlt">hydrate</span> is known to occur at about 50 locations on continental margins (Kvenvolden, 1993) and is certainly far more widespread so it may represent a potentially enormous energy <span class="hlt">resource</span> (Kvenvolden, 1988). But adverse effects related to the presence of <span class="hlt">hydrate</span> do occur. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> appears to have caused slope instabilities along continental margins (Booth et al., 1994; Dillon et al., 1998; Mienert et al., 1998; Paull & Dillon, (Chapter 12; Twichell & Cooper, 2000) and it has also been responsible for drilling accidents (Yakushev and Collett, 1992). Uncontrolled release of methane could affect global climate (Chapter 11), because methane is 15–20 times more effective as a “greenhouse gas” than an equivalent concentration of carbon dioxide. Clearly, a knowledge of <span class="hlt">gas-hydrate</span> properties is necessary to safely explore the possibility of energy recovery and to understand its past and future impact on the geosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10129176','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10129176"><span>Primer on <span class="hlt">gas</span> integrated <span class="hlt">resource</span> planning</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Goldman, C.; Comnes, G.A.; Busch, J.; Wiel, S.</p> <p>1993-12-01</p> <p>This report discusses the following topics: <span class="hlt">gas</span> <span class="hlt">resource</span> planning: need for IRP; <span class="hlt">gas</span> integrated <span class="hlt">resource</span> planning: methods and models; supply and capacity planning for <span class="hlt">gas</span> utilities; methods for estimating <span class="hlt">gas</span> avoided costs; economic analysis of <span class="hlt">gas</span> utility DSM programs: benefit-cost tests; <span class="hlt">gas</span> DSM technologies and programs; end-use fuel substitution; and financial aspects of <span class="hlt">gas</span> demand-side management programs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B13B0621S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B13B0621S"><span>Numerical simulations of CO2 -assisted <span class="hlt">gas</span> production from <span class="hlt">hydrate</span> reservoirs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sridhara, P.; Anderson, B. J.; Myshakin, E. M.</p> <p>2015-12-01</p> <p>A series of experimental studies over the last decade have reviewed the feasibility of using CO2 or CO2+N2 <span class="hlt">gas</span> mixtures to recover CH4 <span class="hlt">gas</span> from <span class="hlt">hydrates</span> deposits. That technique would serve the dual purpose of CO2 sequestration and production of CH4 while maintaining the geo-mechanical stability of the reservoir. In order to analyze CH4 production process by means of CO2 or CO2+N2 injection into <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs, a new simulation tool, Mix3<span class="hlt">Hydrate</span>ResSim (Mix3HRS)[1], was previously developed to account for the complex thermodynamics of multi-component <span class="hlt">hydrate</span> phase and to predict the process of CH4 substitution by CO2 (and N2) in the <span class="hlt">hydrate</span> lattice. In this work, Mix3HRS is used to simulate the CO2 injection into a Class 2 <span class="hlt">hydrate</span> accumulation characterized by a mobile aqueous phase underneath a <span class="hlt">hydrate</span> bearing sediment. That type of <span class="hlt">hydrate</span> reservoir is broadly confirmed in permafrost and along seashore. The production technique implies a two-stage approach using a two-well design, one for an injector and one for a producer. First, the CO2 is injected into the mobile aqueous phase to convert it into immobile CO2 <span class="hlt">hydrate</span> and to initiate CH4 release from <span class="hlt">gas</span> <span class="hlt">hydrate</span> across the <span class="hlt">hydrate</span>-water boundary (generally designating the onset of a <span class="hlt">hydrate</span> stability zone). Second, CH4 <span class="hlt">hydrate</span> decomposition is induced by the depressurization method at a producer to estimate <span class="hlt">gas</span> production potential over 30 years. The conversion of the free water phase into the CO2 <span class="hlt">hydrate</span> significantly reduces competitive water production in the second stage, thereby improving the methane <span class="hlt">gas</span> production. A base case using only the depressurization stage is conducted to compare with enhanced <span class="hlt">gas</span> production predicted by the CO2-assisted technique. The approach also offers a possibility to permanently store carbon dioxide in the underground formation to greater extent comparing to a direct injection of CO2 into <span class="hlt">gas</span> <span class="hlt">hydrate</span> sediment. Numerical models are based on the <span class="hlt">hydrate</span> formations at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10185837','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10185837"><span>Sources of biogenic methane to form marine <span class="hlt">gas</span> <span class="hlt">hydrates</span>: In situ production or upward migration?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Paull, C.K.; Ussler, W. III; Borowski, W.S.</p> <p>1993-09-01</p> <p>Potential sources of biogenic methane in the Carolina Continental Rise -- Blake Ridge sediments have been examined. Two models were used to estimate the potential for biogenic methane production: (1) construction of sedimentary organic carbon budgets, and (2) depth extrapolation of modern microbial production rates. While closed-system estimates predict some <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation, it is unlikely that >3% of the sediment volume could be filled by <span class="hlt">hydrate</span> from methane produced in situ. Formation of greater amounts requires migration of methane from the underlying continental rise sediment prism. Methane may be recycled from below the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone by <span class="hlt">gas</span> <span class="hlt">hydrate</span> decomposition, upward migration of the methane <span class="hlt">gas</span>, and recrystallization of <span class="hlt">gas</span> <span class="hlt">hydrate</span> within the overlying stability zone. Methane bubbles may also form in the sediment column below the depth of <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability because the methane saturation concentration of the pore fluids decreases with increasing depth. Upward migration of methane bubbles from these deeper sediments can add methane to the <span class="hlt">hydrate</span> stability zone. From these models it appears that recycling and upward migration of methane is essential in forming significant <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentrations. In addition, the depth distribution profiles of methane <span class="hlt">hydrate</span> will differ if the majority of the methane has migrated upward rather than having been produced in situ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25358164','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25358164"><span>[Raman spectroscopic studies on CO2-CH4-N2 mixed-<span class="hlt">gas</span> <span class="hlt">hydrate</span> system].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Bao-yong; Liu, Chuan-hai; Wu, Qiang; Gao, Xia</p> <p>2014-06-01</p> <p>Accurate determination of coal mine <span class="hlt">gas</span> separation product characteristics is the key for <span class="hlt">gas</span> separation application based on <span class="hlt">hydrate</span> technology. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> was synthesized from two types of <span class="hlt">gas</span> compositions (CO2-CH4-N2). The separation products were measured by in situ Raman spectroscopy. The crystal structure of mixed-<span class="hlt">gas</span> <span class="hlt">hydrate</span> was determined, and the cavity occupancy and <span class="hlt">hydration</span> index were calculated, based on the object molecular various vibrational mode, "loose cage-tight cage" model and the Raman bands area ratio, combined with the model of van der Waals-Platteeuw. The results show that the mixed-<span class="hlt">gas</span> <span class="hlt">hydrates</span> are both structure I for the two <span class="hlt">gas</span> samples; Large cages of mixed-<span class="hlt">gas</span> <span class="hlt">hydrate</span> are nearly occupied by guest molecules, and the large cavity occupancies are 98.57% and 98.52%, respectively; but small cages are not easy to be occupied, and the small cavity occupancies are 29.93% and 33.87%, respectively; <span class="hlt">hydration</span> index of the two <span class="hlt">gas</span> samples <span class="hlt">hydrate</span> is 7.14 and 6.98, respectively, which is greater than the theoretical value of structure I.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.U23D0079S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.U23D0079S"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> reservoir degassing: thermodynamic and kinetic data as basis for predictions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schicks, J. M.; Girod, M.; Naumann, R.; Erzinger, J.; Horsfield, B.; di Primio, R.</p> <p>2008-12-01</p> <p>Natural <span class="hlt">gas</span> <span class="hlt">hydrates</span> contain predominantly methane but sometimes also other hydrocarbon- and non- hydrocarbon gases such as CO2 or H2S. The amount of other gases beside methane depends on the source of the <span class="hlt">gas</span>: in case of a microbial origin the <span class="hlt">gas</span> is almost pure methane whereas gases from thermal origin may contain a high percentage of higher-molecular weight compounds, such as ethane, propane and larger hydrocarbons. Calculated compositions of <span class="hlt">gas</span> leaking from an oil reservoir also show a significant amount of nitrogen beside the other components. All components in addition to methane have a strong influence on the stability field of the resulting <span class="hlt">hydrate</span> phase. In the presence of higher hydrocarbons the stability of the resulting <span class="hlt">gas</span> <span class="hlt">hydrate</span> is shifted to higher temperatures and lower pressures whereas the enclathration of nitrogen induces a shift of the <span class="hlt">hydrate</span> stability to higher pressures and lower temperatures in comparison to pure methane <span class="hlt">hydrate</span>. Furthermore, <span class="hlt">hydrate</span> formation kinetics also depend on the composition of the <span class="hlt">gas</span> phase: recent studies have shown the rapid formation of <span class="hlt">hydrates</span> containing H2S in addition to methane, whereas the formation of <span class="hlt">hydrates</span> containing small amounts of ethane and propane seemed to be kinetically inhibited. Due to the significant changes in <span class="hlt">hydrate</span> stability and formation kinetics depending on <span class="hlt">gas</span> composition thermodynamic and kinetic data for <span class="hlt">gas</span> mixtures is crucial for all calculations and predictions regarding <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoir degassing as a consequence of climate change. In this study we will present thermodynamic and kinetic data from in-situ measurements (X-ray diffraction and Raman spectroscopy) on <span class="hlt">gas</span> <span class="hlt">hydrates</span> that had been synthesized under natural conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS41E..01P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS41E..01P"><span>Distinctive Geomorphology of <span class="hlt">Gas</span> Venting and Near Seafloor <span class="hlt">Gas</span> <span class="hlt">Hydrate</span>-Bearing sites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paull, C. K.; Caress, D. W.; Lundsten, E.; Anderson, K.; Gwiazda, R.; McGann, M. L.; Edwards, B. D.; Riedel, M.; Herguera, J.</p> <p>2012-12-01</p> <p>High-resolution multibeam bathymetry and chirp seismic-reflection profiles collected with an Autonomous Underwater Vehicle (AUV) complimented by Remotely Operated Vehicle (ROV) observations and sampling reveal the fine scale geomorphology associated with <span class="hlt">gas</span> venting and/or near subsurface <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations along the Pacific North American continental margin (Santa Monica Basin, <span class="hlt">Hydrate</span> Ridge, Eel River, Barkley Canyon, and Bullseye Vent) and along the transform faults in the Gulf of California. At the 1 m multibeam grid resolution of the new data, distinctive features and textures that are undetectable at lower resolution, show the impact of <span class="hlt">gas</span> venting, <span class="hlt">gas</span> <span class="hlt">hydrate</span> development, and related phenomena on the seafloor morphology. Together a suite of geomorphic characteristics illustrates different stages in the development of seafloor <span class="hlt">gas</span> venting systems. The more mature and/or impacted areas are associated with widespread exposures of methane-derived carbonates, which form broken and irregular seafloor pavements with karst-like voids in between the cemented blocks. These mature areas also contain elevated features >10 m high and circular seafloor craters with diameters of 3-50 m that appear to be associated with missing sections of the original seafloor. Smaller mound-like features (<10 m in diameter and 1-3 m higher than the surrounding seafloor) occur at multiple sites. Solid lenses of <span class="hlt">gas</span> <span class="hlt">hydrate</span> are occasionally exposed along fractures on the sides of these mounds and suggest that these are push-up features associated with <span class="hlt">gas</span> <span class="hlt">hydrate</span> growth within the near seafloor sediments. The youngest appearing features are associated with more-subtle (<3 m in diameter and ~0.5 m high) seafloor mounds, the crests of which are crossed with small cracks lined with white bacterial mats. ROV-collected (<1.5 m long) cores obtained from these subtle mounds encountered a hard layer at 30-60 cm sub-bottom. When this layer was penetrated, methane bubbles gushed out and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.1265Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.1265Y"><span>Impact of gravity on <span class="hlt">hydrate</span> saturation in <span class="hlt">gas</span>-rich environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>You, Kehua; DiCarlo, David; Flemings, Peter B.</p> <p>2016-02-01</p> <p>We extend a one-dimensional analytical solution by including buoyancy-driven flow to explore the impact of gravity on <span class="hlt">hydrate</span> formation from <span class="hlt">gas</span> injection into brine-saturated sediments within the <span class="hlt">hydrate</span> stability zone. This solution includes the fully coupled <span class="hlt">gas</span> and liquid phase flow and the associated advective transport in a homogeneous system. We obtain the saturations assuming Darcy flow under combined pressure and gravity gradients; capillary forces are neglected. At a high <span class="hlt">gas</span> supply rate, the overpressure gradient (gradient of water pressure deviation from the hydrostatic pressure) dominates the <span class="hlt">gas</span> flow, and the <span class="hlt">hydrate</span> saturation is independent of the flow rate and flow direction. At a low <span class="hlt">gas</span> supply rate, the buoyancy (the drive for <span class="hlt">gas</span> flow induced by the density difference between <span class="hlt">gas</span> and liquid) dominates the <span class="hlt">gas</span> flow, and the <span class="hlt">hydrate</span> saturation depends on the flow rate and flow direction. <span class="hlt">Hydrate</span> saturation is highest for upward flow, and lowest for downward flow. <span class="hlt">Hydrate</span> saturation decreases with flow rate for upward flow, and increases with flow rate for downward flow. In all cases, <span class="hlt">hydrate</span> saturation is constant behind the <span class="hlt">hydrate</span> solidification front. <span class="hlt">Gas</span> saturation is homogeneous and close to the residual value for upward flow at a low rate; <span class="hlt">gas</span> flows at the rate it is supplied. <span class="hlt">Gas</span> saturation is much greater than the residual value, and decreases from the <span class="hlt">gas</span> inlet to the <span class="hlt">hydrate</span> solidification front for downward flow at a very low rate. The effect of gravity is usually negligible in laboratory experiments, yet is significant in natural <span class="hlt">hydrate</span> systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B22B..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B22B..05K"><span>The relationship between <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation and P-wave velocity of pressure cores obtained in the Eastern Nankai Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Fujii, T.; Nagao, J.</p> <p>2014-12-01</p> <p>P-wave velocity is an important parameter to estimate <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation in sediments. In this study, the relationship between <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation and P-wave velocity have been analyzed using natural <span class="hlt">hydrate</span>-bearing-sediments obtained in the Eastern Nankai Trough, Japan. The sediment samples were collected by the Hybrid Pressure Coring System developed by Japan Agency for Marine-Earth Science and Technology during June-July 2012, aboard the deep sea drilling vessel CHIKYU. P-wave velocity was measured on board by the Pressure Core Analysis and Transfer System developed by Geotek Ltd. The samples were maintained at a near in-situ pressure condition during coring and measurement. After the measurement, the samples were stored core storage chambers and transported to MHRC under pressure. The samples were manipulated and cut by the Pressure-core Non-destructive Analysis Tools or PNATs developed by MHRC. The cutting sections were determined on the basis of P-wave velocity and visual observations through an acrylic window equipped in the PNATs. The cut samples were depressurized to measure <span class="hlt">gas</span> volume for saturation calculations. It was found that P-wave velocity correlates well with <span class="hlt">hydrate</span> saturation and can be reproduced by the <span class="hlt">hydrate</span> frame component model. Using pressure cores and pressure core analysis technology, nondestructive and near in-situ correlation between <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation and P-wave velocity can be obtained. This study was supported by funding from the Research Consortium for Methane <span class="hlt">Hydrate</span> <span class="hlt">Resources</span> in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10147402','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10147402"><span><span class="hlt">Hydrate</span> detection</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dillon, W.P.; Ahlbrandt, T.S.</p> <p>1992-06-01</p> <p>Project objectives were: (1) to create methods of analyzing <span class="hlt">gas</span> <span class="hlt">hydrates</span> in natural sea-floor sediments, using available data, (2) to make estimates of the amount of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in marine sediments, (3) to map the distribution of <span class="hlt">hydrates</span>, (4) to relate concentrations of <span class="hlt">gas</span> <span class="hlt">hydrates</span> to natural processes and infer the factors that control <span class="hlt">hydrate</span> concentration or that result in loss of <span class="hlt">hydrate</span> from the sea floor. (VC)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5287837','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5287837"><span><span class="hlt">Hydrate</span> detection</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dillon, W.P.; Ahlbrandt, T.S.</p> <p>1992-01-01</p> <p>Project objectives were: (1) to create methods of analyzing <span class="hlt">gas</span> <span class="hlt">hydrates</span> in natural sea-floor sediments, using available data, (2) to make estimates of the amount of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in marine sediments, (3) to map the distribution of <span class="hlt">hydrates</span>, (4) to relate concentrations of <span class="hlt">gas</span> <span class="hlt">hydrates</span> to natural processes and infer the factors that control <span class="hlt">hydrate</span> concentration or that result in loss of <span class="hlt">hydrate</span> from the sea floor. (VC)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2008/5219/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2008/5219/"><span>Models for <span class="hlt">Gas</span> <span class="hlt">Hydrate</span>-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lee, Myung W.</p> <p>2008-01-01</p> <p>Elastic velocities and hydraulic permeability of <span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sediments strongly depend on how <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulates in pore spaces and various <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation models are proposed to predict physical property changes due to <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of <span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentration indicates that the dominant effect of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the pore space is the pore-filling characteristic.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2009/5141/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2009/5141/"><span>Anisotropic Velocities of <span class="hlt">Gas</span> <span class="hlt">Hydrate</span>-Bearing Sediments in Fractured Reservoirs</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lee, Myung W.</p> <p>2009-01-01</p> <p>During the Indian National <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Program Expedition 01 (NGHP-01), one of the richest marine <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations was discovered at drill site NGHP-01-10 in the Krishna-Godavari Basin, offshore of southeast India. The occurrence of concentrated <span class="hlt">gas</span> <span class="hlt">hydrate</span> at this site is primarily controlled by the presence of fractures. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations estimated from P- and S-wave velocities, assuming that <span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sediments (GHBS) are isotropic, are much higher than those estimated from the pressure cores. To reconcile this difference, an anisotropic GHBS model is developed and applied to estimate <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations estimated from the P-wave velocities, assuming high-angle fractures, agree well with saturations estimated from the cores. An anisotropic GHBS model assuming two-component laminated media - one component is fracture filled with 100-percent <span class="hlt">gas</span> <span class="hlt">hydrate</span>, and the other component is the isotropic water-saturated sediment - adequately predicts anisotropic velocities at the research site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Natural+AND+gas&pg=3&id=EJ820853','ERIC'); return false;" href="http://eric.ed.gov/?q=Natural+AND+gas&pg=3&id=EJ820853"><span><span class="hlt">Gas</span> Clathrate <span class="hlt">Hydrates</span> Experiment for High School Projects and Undergraduate Laboratories</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Prado, Melissa P.; Pham, Annie; Ferazzi, Robert E.; Edwards, Kimberly; Janda, Kenneth C.</p> <p>2007-01-01</p> <p>We present a laboratory procedure, suitable for high school and undergraduate students, for preparing and studying propane clathrate <span class="hlt">hydrate</span>. Because of their <span class="hlt">gas</span> storage potential and large natural deposits, <span class="hlt">gas</span> clathrate <span class="hlt">hydrates</span> may have economic importance both as an energy source and a transportation medium. Similar to pure ice, the gas…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1996/of96-272/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1996/of96-272/"><span>Offshore <span class="hlt">gas</span> <span class="hlt">hydrate</span> sample database with an overview and preliminary analysis</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Booth, James S.; Rowe, Mary M.; Fisher, Kathleen M.</p> <p>1996-01-01</p> <p>Synopsis -- A database of offshore <span class="hlt">gas</span> <span class="hlt">hydrate</span> samples was constructed from published observations and measurements. More than 90 samples from 15 distinct regions are represented in 13 data categories. This database has permitted preliminary description of <span class="hlt">gas</span> <span class="hlt">hydrate</span> (chiefly methane <span class="hlt">hydrate</span>) tendencies and associations with respect to their geological environment. <span class="hlt">Gas</span> <span class="hlt">hydrates</span> have been recovered from offshore sediment worldwide and from total depths (water depth plus subseabed depth) ranging from 500 m to nearly 6,000 m. Samples have come from subbottom depths ranging from 0 to 400 m. Various physiographic provinces are represented in the data set including second order landforms such as continental margins and deep-sea trenches, and third order forms such as submarine canyons, continental slopes, continental margin ridges and intraslope basins. There is a clear association between fault zones and other manifestations of local, tectonic-related processes, and <span class="hlt">hydrate</span>-bearing sediment. Samples of <span class="hlt">gas</span> <span class="hlt">hydrate</span> frequently consist of individual grains or particles. These types of <span class="hlt">hydrates</span> are often further described as inclusions or disseminated in the sediment. Moreover, <span class="hlt">hydrates</span> occur as a cement, as nodules, or as layers (mostly laminae) or in veins. The preponderance of <span class="hlt">hydrates</span> that could be characterized as 2- dimensional (planar) were associated with fine sediment, either as intercalated layers or in fractures. <span class="hlt">Hydrate</span> cements were commonly associated with coarser sediment. <span class="hlt">Hydrates</span> have been found in association with grain sizes ranging from clay through gravel. More <span class="hlt">hydrates</span> are associated with the more abundant finer-grained sediment than with coarser sediment, and many were discovered in the presence of both fine (silt and clay) and coarse sediment. The thickness of <span class="hlt">hydrate</span> zones (i. e., sections of <span class="hlt">hydrate</span>-bearing sediment) varies from a few centimeters to as much as 30 m. In contrast, the thickness of layers of pure <span class="hlt">hydrate</span> or the dimensions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B13B0603R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B13B0603R"><span>Characterization of <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> Formation and Dissociation Using Thermal Analysis and Calorimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rudow, M.; Lilova, K.</p> <p>2015-12-01</p> <p>In general, the <span class="hlt">gas</span> <span class="hlt">hydrates</span> are formed at low temperature and high pressure which requires a special technique to mimic the natural conditions. The <span class="hlt">hydrate</span> thermal properties: heat capacity, heat of dissociation, are crucial for evaluating the effects on climate change and for a prediction of the <span class="hlt">gas</span> production rates from <span class="hlt">hydrate</span> reservoirs. The effect of the porous materials on the dissociation of synthetic methane <span class="hlt">hydrates</span> was investigated at 150 - 300 K and atmospheric pressure. Another experiment with methane <span class="hlt">hydrates</span>, but at high pressure (20 MPa) was performed at near room temperature using a highly sensitive micro-differential scanning calorimeter with a specifically design high pressure vessel (the vessel can withstand a pressure up to 1000 bars). The thermal cycle for measuring the methane <span class="hlt">hydrate</span> dissociation in water includes cooling down a water solution under a certain methane pressure (30 to 350 bars) to -30 C to allow water crystallization and <span class="hlt">hydrate</span> formation, then heated up to room temperature. The endothermic peak, following the ice melting is associated to the <span class="hlt">hydrate</span> dissociation process and gives the enthalpy of the <span class="hlt">hydrate</span> decomposition. The kinetics of the <span class="hlt">hydrates</span> formation could also be predicted by a rapid DSC cooling experiment followed by isothermal step and heating. Both dissociation and specific heats of synthetic methane and ethane <span class="hlt">hydrates</span> were measured under high-pressure condition by using a heat-flow type calorimeter to understand thermodynamic properties of <span class="hlt">gas</span> <span class="hlt">hydrates</span> under submarine/sublacustrine environments. The large reserves of natural <span class="hlt">gas</span> are present as clathrate <span class="hlt">hydrates</span> in permafrost regions and beneath the oceans have generated interest in the study of their thermophysical properties such as heat capacity and thermal conductivity. The effect of isotopic substitution in both THF and water on the eutectic and <span class="hlt">hydrate</span> melting temperatures in water-tetrahydrofuran systems studied by DSC will be shown as an example.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026707','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026707"><span>Scanning electron microscopy investigations of laboratory-grown <span class="hlt">gas</span> clathrate <span class="hlt">hydrates</span> formed from melting ice, and comparison to natural <span class="hlt">hydrates</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stern, L.A.; Kirby, S.H.; Circone, S.; Durham, W.B.</p> <p>2004-01-01</p> <p>Scanning electron microscopy (SEM) was used to investigate grain texture and pore structure development within various compositions of pure sI and sII <span class="hlt">gas</span> <span class="hlt">hydrates</span> synthesized in the laboratory, as well as in natural samples retrieved from marine (Gulf of Mexico) and permafrost (NW Canada) settings. Several samples of methane <span class="hlt">hydrate</span> were also quenched after various extents of partial reaction for assessment of mid-synthesis textural progression. All laboratory-synthesized <span class="hlt">hydrates</span> were grown under relatively high-temperature and high-pressure conditions from rounded ice grains with geometrically simple pore shapes, yet all resulting samples displayed extensive recrystallization with complex pore geometry. Growth fronts of mesoporous methane <span class="hlt">hydrate</span> advancing into dense ice reactant were prevalent in those samples quenched after limited reaction below and at the ice point. As temperatures transgress the ice point, grain surfaces continue to develop a discrete "rind" of <span class="hlt">hydrate</span>, typically 5 to 30 ??m thick. The cores then commonly melt, with rind microfracturing allowing migration of the melt to adjacent grain boundaries where it also forms <span class="hlt">hydrate</span>. As the reaction continues under progressively warmer conditions, the <span class="hlt">hydrate</span> product anneals to form dense and relatively pore-free regions of <span class="hlt">hydrate</span> grains, in which grain size is typically several tens of micrometers. The prevalence of hollow, spheroidal shells of <span class="hlt">hydrate</span>, coupled with extensive redistribution of reactant and product phases throughout reaction, implies that a diffusion-controlled shrinking-core model is an inappropriate description of sustained <span class="hlt">hydrate</span> growth from melting ice. Completion of reaction at peak synthesis conditions then produces exceptional faceting and euhedral crystal growth along exposed pore walls. Further recrystallization or regrowth can then accompany even short-term exposure of synthetic <span class="hlt">hydrates</span> to natural ocean-floor conditions, such that the final textures may closely mimic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/973382','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/973382"><span>Occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in Oligocene Frio sand: Alaminos Canyon Block 818: Northern Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Boswell, R.D.; Shelander, D.; Lee, M.; Latham, T.; Collett, T.; Guerin, G.; Moridis, G.; Reagan, M.; Goldberg, D.</p> <p>2009-07-15</p> <p>A unique set of high-quality downhole shallow subsurface well log data combined with industry standard 3D seismic data from the Alaminos Canyon area has enabled the first detailed description of a concentrated <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation within sand in the Gulf of Mexico. The <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurs within very fine grained, immature volcaniclastic sands of the Oligocene Frio sand. Analysis of well data acquired from the Alaminos Canyon Block 818 No.1 ('Tigershark') well shows a total <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence 13 m thick, with inferred <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation as high as 80% of sediment pore space. Average porosity in the reservoir is estimated from log data at approximately 42%. Permeability in the absence of <span class="hlt">gas</span> <span class="hlt">hydrates</span>, as revealed from the analysis of core samples retrieved from the well, ranges from 600 to 1500 millidarcies. The 3-D seismic data reveals a strong reflector consistent with significant increase in acoustic velocities that correlates with the top of the <span class="hlt">gas-hydrate</span>-bearing sand. This reflector extends across an area of approximately 0.8 km{sup 2} and delineates the minimal probable extent of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation. The base of the inferred <span class="hlt">gas-hydrate</span> zone also correlates well with a very strong seismic reflector that indicates transition into units of significantly reduced acoustic velocity. Seismic inversion analyses indicate uniformly high <span class="hlt">gas-hydrate</span> saturations throughout the region where the Frio sand exists within the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Numerical modeling of the potential production of natural <span class="hlt">gas</span> from the interpreted accumulation indicates serious challenges for depressurization-based production in settings with strong potential pressure support from extensive underlying aquifers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036826','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036826"><span>Occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in Oligocene Frio sand: Alaminos Canyon Block 818: Northern Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Boswell, R.; Shelander, D.; Lee, M.; Latham, T.; Collett, T.; Guerin, G.; Moridis, G.; Reagan, M.; Goldberg, D.</p> <p>2009-01-01</p> <p>A unique set of high-quality downhole shallow subsurface well log data combined with industry standard 3D seismic data from the Alaminos Canyon area has enabled the first detailed description of a concentrated <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation within sand in the Gulf of Mexico. The <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurs within very fine grained, immature volcaniclastic sands of the Oligocene Frio sand. Analysis of well data acquired from the Alaminos Canyon Block 818 #1 ("Tigershark") well shows a total <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence 13??m thick, with inferred <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation as high as 80% of sediment pore space. Average porosity in the reservoir is estimated from log data at approximately 42%. Permeability in the absence of <span class="hlt">gas</span> <span class="hlt">hydrates</span>, as revealed from the analysis of core samples retrieved from the well, ranges from 600 to 1500 millidarcies. The 3-D seismic data reveals a strong reflector consistent with significant increase in acoustic velocities that correlates with the top of the <span class="hlt">gas-hydrate</span>-bearing sand. This reflector extends across an area of approximately 0.8??km2 and delineates the minimal probable extent of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation. The base of the inferred <span class="hlt">gas-hydrate</span> zone also correlates well with a very strong seismic reflector that indicates transition into units of significantly reduced acoustic velocity. Seismic inversion analyses indicate uniformly high <span class="hlt">gas-hydrate</span> saturations throughout the region where the Frio sand exists within the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Numerical modeling of the potential production of natural <span class="hlt">gas</span> from the interpreted accumulation indicates serious challenges for depressurization-based production in settings with strong potential pressure support from extensive underlying aquifers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/936573','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/936573"><span>Site Selection for DOE/JIP <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Drilling in the Northern Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hutchinson, D.R.; Shelander, D.; Dai, J.; McConnell, D.; Shedd, W.; Frye, M.; Ruppel, C.; Boswell, R.; Jones, E.; Collett, T.S.; Rose, K.; Dugan, B.; Wood, W.; Latham, T.</p> <p>2008-07-01</p> <p>In the late spring of 2008, the Chevron-led Gulf of Mexico <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Joint Industry Project (JIP) expects to conduct an exploratory drilling and logging campaign to better understand <span class="hlt">gas</span> <span class="hlt">hydrate</span>-bearing sands in the deepwater Gulf of Mexico. The JIP Site Selection team selected three areas to test alternative geological models and geophysical interpretations supporting the existence of potential high <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations in reservoir-quality sands. The three sites are near existing drill holes which provide geological and geophysical constraints in Alaminos Canyon (AC) lease block 818, Green Canyon (GC) 955, and Walker Ridge (WR) 313. At the AC818 site, <span class="hlt">gas</span> <span class="hlt">hydrate</span> is interpreted to occur within the Oligocene Frio volcaniclastic sand at the crest of a fold that is shallow enough to be in the <span class="hlt">hydrate</span> stability zone. Drilling at GC955 will sample a faulted, buried Pleistocene channel-levee system in an area characterized by seafloor fluid expulsion features, structural closure associated with uplifted salt, and abundant seismic evidence for upward migration of fluids and <span class="hlt">gas</span> into the sand-rich parts of the sedimentary section. Drilling at WR313 targets ponded sheet sands and associated channel/levee deposits within a minibasin, making this a non-structural play. The potential for <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence at WR313 is supported by shingled phase reversals consistent with the transition from <span class="hlt">gas</span>-charged sand to overlying <span class="hlt">gas-hydrate</span> saturated sand. Drilling locations have been selected at each site to 1) test geological methods and models used to infer the occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in sand reservoirs in different settings in the northern Gulf of Mexico; 2) calibrate geophysical models used to detect <span class="hlt">gas</span> <span class="hlt">hydrate</span> sands, map reservoir thicknesses, and estimate the degree of <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation; and 3) delineate potential locations for subsequent JIP drilling and coring operations that will collect samples for comprehensive physical property, geochemical and other</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRB..116.8202J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRB..116.8202J"><span>Recoverable <span class="hlt">gas</span> from <span class="hlt">hydrate</span>-bearing sediments: Pore network model simulation and macroscale analyses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jang, Jaewon; Santamarina, J. Carlos</p> <p>2011-08-01</p> <p>The volume of <span class="hlt">hydrate</span> expands into a significantly larger volume of water and <span class="hlt">gas</span> upon dissociation. <span class="hlt">Gas</span> recovery and capillary-trapped residual <span class="hlt">gas</span> saturation are investigated by simulating <span class="hlt">hydrate</span> dissociation within pore networks. A fluid pressure-controlled boundary condition is used to determine the amount of recovered <span class="hlt">gas</span> as a function of volume expansion; in this form, results are applicable to <span class="hlt">gas</span> production by either thermal stimulation or depressurization when production rates prevent secondary <span class="hlt">hydrate</span> or ice formation. Simulation results show that <span class="hlt">gas</span> recovery is proportional to <span class="hlt">gas</span> expansion, initial <span class="hlt">hydrate</span> saturation, and the sediment pore size distribution (i.e., capillary pressure). <span class="hlt">Gas</span> recovery is not affected by pore size in coarse-grained sediments with pores larger than 1 μm. <span class="hlt">Hydrate</span>-bearing sediments with low <span class="hlt">hydrate</span> saturation yield low <span class="hlt">gas</span> recovery. Macroscale close form solutions, validated using the numerical results, provide estimates for recoverable <span class="hlt">gas</span> as a function of the initial <span class="hlt">hydrate</span> saturation and the fluid expansion factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25785915','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25785915"><span>Micromechanical cohesion force between <span class="hlt">gas</span> <span class="hlt">hydrate</span> particles measured under high pressure and low temperature conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Bo Ram; Sum, Amadeu K</p> <p>2015-04-07</p> <p>To prevent <span class="hlt">hydrate</span> plugging conditions in the transportation of oil/<span class="hlt">gas</span> in multiphase flowlines, one of the key processes to control is the agglomeration/deposition of <span class="hlt">hydrate</span> particles, which are determined by the cohesive/adhesive forces. Previous studies reporting measurements of the cohesive/adhesive force between <span class="hlt">hydrate</span> particles used cyclopentane <span class="hlt">hydrate</span> particles in a low-pressure micromechanical force apparatus. In this study, we report the cohesive forces of particles measured in a new high-pressure micromechanical force (MMF) apparatus for ice particles, mixed (methane/ethane, 74.7:25.3) <span class="hlt">hydrate</span> particles (Structure II), and carbon dioxide <span class="hlt">hydrate</span> particles (Structure I). The cohesive forces are measured as a function of the contact time, contact force, temperature, and pressure, and determined from pull-off measurements. For the measurements performed of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> particles in the <span class="hlt">gas</span> phase, the determined cohesive force is about 30-35 mN/m, about 8 times higher than the cohesive force of CyC5 <span class="hlt">hydrates</span> in the liquid CyC5, which is about 4.3 mN/m. We show from our results that the <span class="hlt">hydrate</span> structure (sI with CO2 <span class="hlt">hydrates</span> and sII with CH4/C2H6 <span class="hlt">hydrates</span>) has no influence on the cohesive force. These results are important in the deposition of a <span class="hlt">gas</span>-dominated system, where the <span class="hlt">hydrate</span> particles formed in the liquid phase can then stick to the <span class="hlt">hydrate</span> deposited in the wall exposed to the <span class="hlt">gas</span> phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040061999&hterms=gas+hydrates+mars&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgas%2Bhydrates%2Bmars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040061999&hterms=gas+hydrates+mars&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgas%2Bhydrates%2Bmars"><span><span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stability at Low Temperatures and High Pressures with Applications to Mars and Europa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marion, G. M.; Kargel, J. S.; Catling, D. C.</p> <p>2004-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> are implicated in the geochemical evolution of both Mars and Europa [1- 3]. Most models developed for <span class="hlt">gas</span> <span class="hlt">hydrate</span> chemistry are based on the statistical thermodynamic model of van der Waals and Platteeuw [4] with subsequent modifications [5-8]. None of these models are, however, state-of-the-art with respect to <span class="hlt">gas</span> <span class="hlt">hydrate</span>/electrolyte interactions, which is particularly important for planetary applications where solution chemistry may be very different from terrestrial seawater. The objectives of this work were to add <span class="hlt">gas</span> (carbon dioxide and methane) <span class="hlt">hydrate</span> chemistries into an electrolyte model parameterized for low temperatures and high pressures (the FREZCHEM model) and use the model to examine controls on <span class="hlt">gas</span> <span class="hlt">hydrate</span> chemistries for Mars and Europa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/958940','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/958940"><span>A multi-phase, micro-dispersion reactor for the continuous production of methane <span class="hlt">gas</span> <span class="hlt">hydrate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Taboada Serrano, Patricia L; Ulrich, Shannon M; Szymcek, Phillip; McCallum, Scott; Phelps, Tommy Joe; Palumbo, Anthony Vito; Tsouris, Costas</p> <p>2009-01-01</p> <p>A continuous-jet <span class="hlt">hydrate</span> reactor originally developed to generate a CO2 <span class="hlt">hydrate</span> stream has been modified to continuously produce CH4 <span class="hlt">hydrate</span>. The reactor has been tested in the Seafloor Process Simulator (SPS), a 72-L pressure vessel available at Oak Ridge National Laboratory. During experiments, the reactor was submerged in water inside the SPS and received water from the surrounding through a submersible pump and CH4 externally through a <span class="hlt">gas</span> booster pump. Thermodynamic conditions in the <span class="hlt">hydrate</span> stability regime were employed in the experiments. The reactor produced a continuous stream of CH4 <span class="hlt">hydrate</span>, and based on pressure values and amount of <span class="hlt">gas</span> injected, the conversion of <span class="hlt">gas</span> to <span class="hlt">hydrate</span> was estimated. A conversion of up to 70% was achieved using this reactor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021432','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021432"><span>Elastic-wave velocity in marine sediments with <span class="hlt">gas</span> <span class="hlt">hydrates</span>: Effective medium modeling</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.</p> <p>1999-01-01</p> <p>We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of <span class="hlt">gas</span> <span class="hlt">hydrate</span> on sediment elastic moduli we use two separate assumptions: (a) <span class="hlt">hydrate</span> modifies the pore fluid elastic properties without affecting the frame; (b) <span class="hlt">hydrate</span> becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of <span class="hlt">hydrate</span> in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain <span class="hlt">hydrate</span> concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved <span class="hlt">gas</span> data. Copyright 1999 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70037507','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70037507"><span>Seismic imaging of a fractured <span class="hlt">gas</span> <span class="hlt">hydrate</span> system in the Krishna-Godavari Basin offshore India</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Riedel, M.; Collett, T.S.; Kumar, P.; Sathe, A.V.; Cook, A.</p> <p>2010-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrate</span> was discovered in the Krishna-Godavari (KG) Basin during the India National <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Program (NGHP) Expedition 1 at Site NGHP-01-10 within a fractured clay-dominated sedimentary system. Logging-while-drilling (LWD), coring, and wire-line logging confirmed <span class="hlt">gas</span> <span class="hlt">hydrate</span> dominantly in fractures at four borehole sites spanning a 500m transect. Three-dimensional (3D) seismic data were subsequently used to image the fractured system and explain the occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> associated with the fractures. A system of two fault-sets was identified, part of a typical passive margin tectonic setting. The LWD-derived fracture network at Hole NGHP-01-10A is to some extent seen in the seismic data and was mapped using seismic coherency attributes. The fractured system around Site NGHP-01-10 extends over a triangular-shaped area of ~2.5 km2 defined using seismic attributes of the seafloor reflection, as well as " seismic sweetness" at the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence zone. The triangular shaped area is also showing a polygonal (nearly hexagonal) fault pattern, distinct from other more rectangular fault patterns observed in the study area. The occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> at Site NGHP-01-10 is the result of a specific combination of tectonic fault orientations and the abundance of free <span class="hlt">gas</span> migration from a deeper <span class="hlt">gas</span> source. The triangular-shaped area of enriched <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence is bound by two faults acting as migration conduits. Additionally, the fault-associated sediment deformation provides a possible migration pathway for the free <span class="hlt">gas</span> from the deeper <span class="hlt">gas</span> source into the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. It is proposed that there are additional locations in the KG Basin with possible <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation of similar tectonic conditions, and one such location was identified from the 3D seismic data ~6 km NW of Site NGHP-01-10. ?? 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036007','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036007"><span><span class="hlt">Gas</span> production from a cold, stratigraphically-bounded <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposit at the Mount Elbert <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stratigraphic Test Well, Alaska North Slope: Implications of uncertainties</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Moridis, G.J.; Silpngarmlert, S.; Reagan, M.T.; Collett, T.; Zhang, K.</p> <p>2011-01-01</p> <p>As part of an effort to identify suitable targets for a planned long-term field test, we investigate by means of numerical simulation the <span class="hlt">gas</span> production potential from unit D, a stratigraphically bounded (Class 3) permafrost-associated <span class="hlt">hydrate</span> occurrence penetrated in the BPXA-DOE-USGS Mount Elbert <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stratigraphic Test Well on North Slope, Alaska. This shallow, low-pressure deposit has high porosities (?? = 0.4), high intrinsic permeabilities (k = 10-12 m2) and high <span class="hlt">hydrate</span> saturations (SH = 0.65). It has a low temperature (T = 2.3-2.6 ??C) because of its proximity to the overlying permafrost. The simulation results indicate that vertical wells operating at a constant bottomhole pressure would produce at very low rates for a very long period. Horizontal wells increase <span class="hlt">gas</span> production by almost two orders of magnitude, but production remains low. Sensitivity analysis indicates that the initial deposit temperature is by the far the most important factor determining production performance (and the most effective criterion for target selection) because it controls the sensible heat available to fuel dissociation. Thus, a 1 ??C increase in temperature is sufficient to increase the production rate by a factor of almost 8. Production also increases with a decreasing <span class="hlt">hydrate</span> saturation (because of a larger effective permeability for a given k), and is favored (to a lesser extent) by anisotropy. ?? 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/760361','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/760361"><span>NATURAL <span class="hlt">GAS</span> <span class="hlt">HYDRATES</span> STORAGE PROJECT PHASE II. CONCEPTUAL DESIGN AND ECONOMIC STUDY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>R.E. Rogers</p> <p>1999-09-27</p> <p>DOE Contract DE-AC26-97FT33203 studied feasibility of utilizing the natural-<span class="hlt">gas</span> storage property of <span class="hlt">gas</span> <span class="hlt">hydrates</span>, so abundantly demonstrated in nature, as an economical industrial process to allow expanded use of the clean-burning fuel in power plants. The laboratory work achieved breakthroughs: (1) <span class="hlt">Gas</span> <span class="hlt">hydrates</span> were found to form orders of magnitude faster in an unstirred system with surfactant-water micellar solutions. (2) <span class="hlt">Hydrate</span> particles were found to self-pack by adsorption on cold metal surfaces from the micellar solutions. (3) Interstitial micellar-water of the packed particles were found to continue forming <span class="hlt">hydrates</span>. (4) Aluminum surfaces were found to most actively collect the <span class="hlt">hydrate</span> particles. These laboratory developments were the bases of a conceptual design for a large-scale process where simplification enhances economy. In the design, <span class="hlt">hydrates</span> form, store, and decompose in the same tank in which <span class="hlt">gas</span> is pressurized to 550 psi above unstirred micellar solution, chilled by a brine circulating through a bank of aluminum tubing in the tank employing <span class="hlt">gas</span>-fired refrigeration. <span class="hlt">Hydrates</span> form on aluminum plates suspended in the chilled micellar solution. A low-grade heat source, such as 110 F water of a power plant, circulates through the tubing bank to release stored <span class="hlt">gas</span>. The design allows a formation/storage/decomposition cycle in a 24-hour period of 2,254,000 scf of natural <span class="hlt">gas</span>; the capability of multiple cycles is an advantage of the process. The development costs and the user costs of storing natural <span class="hlt">gas</span> in a scaled <span class="hlt">hydrate</span> process were estimated to be competitive with conventional storage means if multiple cycles of <span class="hlt">hydrate</span> storage were used. If more than 54 cycles/year were used, <span class="hlt">hydrate</span> development costs per Mscf would be better than development costs of depleted reservoir storage; above 125 cycles/year, <span class="hlt">hydrate</span> user costs would be lower than user costs of depleted reservoir storage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28249494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28249494"><span>High pressure rheology of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formed from multiphase systems using modified Couette rheometer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S</p> <p>2017-02-01</p> <p>Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as <span class="hlt">gas</span> <span class="hlt">hydrates</span>. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane <span class="hlt">hydrate</span> formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any <span class="hlt">hydrates</span> in situ and thus failed to measure rheological properties during <span class="hlt">hydrate</span> formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming <span class="hlt">gas</span> <span class="hlt">hydrate</span> from the <span class="hlt">gas</span>-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure <span class="hlt">gas</span> <span class="hlt">hydrate</span> viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of <span class="hlt">hydrate</span> slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the <span class="hlt">hydrate</span> dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formed from various systems containing promoters and inhibitors in the context of flow assurance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RScI...88b5102P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RScI...88b5102P"><span>High pressure rheology of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formed from multiphase systems using modified Couette rheometer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S.</p> <p>2017-02-01</p> <p>Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as <span class="hlt">gas</span> <span class="hlt">hydrates</span>. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane <span class="hlt">hydrate</span> formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any <span class="hlt">hydrates</span> in situ and thus failed to measure rheological properties during <span class="hlt">hydrate</span> formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming <span class="hlt">gas</span> <span class="hlt">hydrate</span> from the <span class="hlt">gas</span>-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure <span class="hlt">gas</span> <span class="hlt">hydrate</span> viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of <span class="hlt">hydrate</span> slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the <span class="hlt">hydrate</span> dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formed from various systems containing promoters and inhibitors in the context of flow assurance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS43F..06Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS43F..06Y"><span>Overview of the 2006-2008 JOGMEC/NRCan/Aurora Mallik <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Production Test Program</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, K.; Dallimore, S. R.</p> <p>2008-12-01</p> <p>During the winters of 2007 and 2008 the Japan Oil, <span class="hlt">Gas</span> and Metals National Corporation (JOGMEC) and Natural <span class="hlt">Resources</span> Canada (NRCan), with Aurora Research Institute as the operator, carried out an on-shore <span class="hlt">gas</span> <span class="hlt">hydrate</span> production test program at the Mallik site, Mackenzie Delta, Northwest Territories, Canada. The prime objective of the program was to verify the feasibility of depressurization technique by drawing down the formation pressure across a 12m perforated <span class="hlt">gas</span> <span class="hlt">hydrate</span> bearing section. This project was the second full scale production test at this site following the 2002 Japex/JNOC/GSC et al Mallik research program in which seven participants organizatinos from five countries undertook a thermal test using hot water circulation Field work in 2007 was devoted to establishing a production test well, installing monitoring devices outside of casing, conducting base line geophysical studies and undertaking a short test to gain practical experience prior to longer term testing planned for 2008 . <span class="hlt">Hydrate</span>-dissociated <span class="hlt">gas</span> was produced to surface by depressurization achieved by lowering the fluid level with a dowhole pump. However, the operation was terminated 60 hours after the start of the pumping mainly due to sand production problems. In spite of the short period (12.5 hours of ellapsed pumping time), at least 830m3 of the <span class="hlt">gas</span> was produced and accumulated in the borehole. Sand screens were installed across the perforated interval at the bottom hole for the 2008 program to overcome operational problems encountered in 2007 and achieve sustainable <span class="hlt">gas</span> production. Stable bottom hole flowing pressures were successfully achieved during a 6 day test with continuous pump operation. Sustained <span class="hlt">gas</span> production was achieved with rates between 2000- 4000m3/day and cummulative <span class="hlt">gas</span> volume in the surface of approximately 13,000m3. Temperature and pressure data measured at the bottom hole and <span class="hlt">gas</span> and water production rates gave positive evidence for the high efficiency of <span class="hlt">gas</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6177614','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6177614"><span>Geologic interrelations relative to <span class="hlt">gas</span> <span class="hlt">hydrates</span> within the North Slope of Alaska: Task No. 6, Final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Collett, T.S.; Bird, K.J.; Kvenvolden, K.A.; Magoon, L.B.</p> <p>1988-01-01</p> <p>The five primary objectives of the US Geological Survey North Slope <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Project were to: (1) Determine possible geologic controls on the occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span>; (2) locate and evaluate possible <span class="hlt">gas-hydrate</span>-bearing reservoirs; (3) estimate the volume of <span class="hlt">gas</span> within the <span class="hlt">hydrates</span>; (4) develop a model for <span class="hlt">gas-hydrate</span> formation; and (5) select a coring site for <span class="hlt">gas-hydrate</span> sampling and analysis. Our studies of the North Slope of Alaska suggest that the zone in which <span class="hlt">gas</span> <span class="hlt">hydrates</span> are stable is controlled primarily by subsurface temperatures and <span class="hlt">gas</span> chemistry. Other factors, such as pore-pressure variations, pore-fluid salinity, and reservior-rock grain size, appear to have little effect on <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability on the North Slope. Data necessary to determine the limits of <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability field are difficult to obtain. On the basis of mud-log <span class="hlt">gas</span> chromatography, core data, and cuttings data, methane is the dominant species of <span class="hlt">gas</span> in the near-surface (0--1500 m) sediment. <span class="hlt">Gas</span> <span class="hlt">hydrates</span> were identified in 34 wells utilizing well-log responses calibrated to the response of an interval in one well where <span class="hlt">gas</span> <span class="hlt">hydrates</span> were actually recovered in a core by an oil company. A possible scenario describing the origin of the interred <span class="hlt">gas</span> <span class="hlt">hydrates</span> on the North Slope involves the migration of thermogenic solution- and free-<span class="hlt">gas</span> from deeper reservoirs upward along faults into the overlying sedimentary rocks. We have identified two (dedicated) core-hole sites, the Eileen and the South-End core-holes, at which there is a high probability of recovering a sample of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. At the Eileen core-hole site, at least three stratigraphic units may contain <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The South-End core-hole site provides an opportunity to study one specific rock unit that appears to contain both <span class="hlt">gas</span> <span class="hlt">hydrate</span> and oil. 100 refs., 72 figs., 24 tabs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024198','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024198"><span><span class="hlt">Resource</span>-assessment perspectives for unconventional <span class="hlt">gas</span> systems</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Schmoker, J.W.</p> <p>2002-01-01</p> <p>Concepts are described for assessing those unconventional <span class="hlt">gas</span> systems that can also be defined as continous accumulations. Continuous <span class="hlt">gas</span> accumulations exist more or less independently of the water column and do not owe their existence directly to the bouyancy of <span class="hlt">gas</span> in water. They cannot be represented in terms of individual, countable fields or pools delineated by downdip water contacts. For these reasons, traditional <span class="hlt">resource</span>-assessment methods based on estimating the sizes and numbers of undiscovered discrete fields cannot not be applied to continuous accumulations. Specialized assessment methods are required. Unconventional <span class="hlt">gas</span> systems that are also continous accumulations include coalbed methane, basin-centered <span class="hlt">gas</span>, so-called tight <span class="hlt">gas</span>, fractured shale (and chalk) <span class="hlt">gas</span>, and <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Deep-basin and bacterial <span class="hlt">gas</span> systems may or may not be continuous accumulations, depending on their geologic setting. Two basic <span class="hlt">resource</span>-assessment approaches have been employed for continous accumulations. The first approach is based on estimates of <span class="hlt">gas</span> in place. A volumetric estimate of total <span class="hlt">gas</span> in place is commonly coupled with an overall recovery factor to narrow the assessment scope from a treatment of <span class="hlt">gas</span> volumes residing in sedimentary strata to a prediction of potential additions to reserves. The second approach is based on the production performance of continous <span class="hlt">gas</span> reservoirs, as shown empirically by wells and reservoir-simulation models. In these methods, production characteristics (as opposed to <span class="hlt">gas</span> in place) are the foundation for forecasts of potential additions to reserves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS21A1608H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS21A1608H"><span>Pore scale distribution of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in sediments by micro X-ray Computed Tomography (X-CT)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, G.; Li, C.; Ye, Y.; Liu, C.; Best, A. I.</p> <p>2013-12-01</p> <p>A dedicated apparatus was developed to observe in-situ pore scale distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> directly during <span class="hlt">hydrate</span> formation in artificial cores. The high-resolution X-ray Computed Tomography (type: GE Sensing & Inspection Technologies GmbH Phoenix x-ray V/tomex/s) was used and the effective resolution for observing <span class="hlt">gas</span> <span class="hlt">hydrate</span> bearing sediments can up to about 18μm. Methane <span class="hlt">gas</span> <span class="hlt">hydrate</span> was formed in 0.425-0.85mm sands under a pressure of 6MPa and a temperature of 3°C. During the process, CT scanning was conducted if there's a pressure drop (the scanning time is 66 minutes each time), so that the <span class="hlt">hydrate</span> morphology could be detected. As a result, five scanning CT images of the same section during <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation (i.e. <span class="hlt">hydrate</span> saturation at 3.9%, 24.6%, 35.0%, 51.4% and 97.0%) were obtained. The result shows that at each <span class="hlt">hydrate</span> saturation level, <span class="hlt">hydrate</span> morphology models are complicated. The occurrence of 'floating model' (i.e. <span class="hlt">hydrate</span> floats in pore fluid), 'contact model' (i.e. <span class="hlt">hydrate</span> contact with the sediment particle), and the 'cementing model' (i.e. <span class="hlt">hydrates</span> cement the sediment particles) can be found at the same time (Fig. 1). However, it shows that at different <span class="hlt">hydrate</span> formation stages, the dominant <span class="hlt">hydrate</span> morphology are not the same. For instance, at the first stage of <span class="hlt">hydrate</span> formation, although there are some <span class="hlt">hydrates</span> floating in the pore fluid, most <span class="hlt">hydrates</span> connect the sediment particles. Consequently, the <span class="hlt">hydrate</span> morphology at this moment can be described as a cementing model. With this method, it can be obtained that at the higher level of saturation (e.g., <span class="hlt">hydrate</span> saturation at 24.6% and 35.0%), <span class="hlt">hydrates</span> are mainly grow as a floating model. As <span class="hlt">hydrate</span> saturation is much higher (e.g. after <span class="hlt">hydrate</span> saturation is more than 51.4%), however, the floating <span class="hlt">hydrates</span> coalesce with each other and the <span class="hlt">hydrates</span> cement the sediment particle again. The direct observed <span class="hlt">hydrate</span> morphology presented here may have significant impact on investigating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS31B..03L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS31B..03L"><span>Addressing Factors that Control Near-Surface <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stability with Time-Series Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lapham, L.; Wilson, R. M.; Chanton, J.; Riedel, M.</p> <p>2015-12-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> are sensitive to pressure and temperature changes, based on their thermodynamic properties. In nature, this translates to changes in sealevel and/or ocean water temperature fluctuations. When <span class="hlt">hydrates</span> outcrop the seafloor, however, they could also be sensitive to physical disturbances, such as earthquakes, and microbial processes (such as sulfate reduction and/or methane oxidation), both of which could lead to their dissolution. To address these factors controlling <span class="hlt">hydrate</span> stability, we will present in situ methane, sulfate, and chloride concentrations over time, in pore-waters of shallow sediments near <span class="hlt">gas</span> <span class="hlt">hydrates</span> in seep systems. Datasets presented will include one 4-month time series from the Northern Gulf of Mexico, Mississippi Canyon 118, and two 9-month records from offshore Vancouver Island, Barkley Canyon and Bubbly Gulch at Bullseye Vent. We will address the following questions: Does regional scale oceanography affect methane flux from the <span class="hlt">hydrate</span>-containing sediments, are microbial processes playing a role in <span class="hlt">hydrate</span> stability, and what are in situ <span class="hlt">hydrate</span> dissolution rates? We will also discuss challenges faced with collecting such data, and ways to move forward. We will show that in some systems, methane is nearly saturated within a few cm of the overlying water, thus stabilizing the <span class="hlt">hydrate</span>. Yet in other systems, methane is undersaturated with respect to methane <span class="hlt">hydrate</span> which suggests <span class="hlt">hydrates</span> will dissolve. We will also present laboratory rates of <span class="hlt">hydrate</span> dissolution to compare to those gained from the field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036952','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036952"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> drilling transect across northern Cascadia margin - IODP Expedition 311</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Riedel, M.; Collett, T.; Malone, M.J.; Collett, T.S.; Mitchell, M.; Guerin, G.; Akiba, F.; Blanc-Valleron, M.; Ellis, M.; Hashimoto, Y.; Heuer, V.; Higashi, Y.; Holland, M.; Jackson, P.D.; Kaneko, M.; Kastner, M.; Kim, J.-H.; Kitajima, H.; Long, P.E.; Malinverno, A.; Myers, Gwen E.; Palekar, L.D.; Pohlman, J.; Schultheiss, P.; Teichert, B.; Torres, M.E.; Trehu, A.M.; Wang, Jingyuan; Worthmann, U.G.; Yoshioka, H.</p> <p>2009-01-01</p> <p>A transect of four sites (U1325, U1326, U1327 and U1329) across the northern Cascadia margin was established during Integrated Ocean Drilling Program Expedition 311 to study the occurrence and formation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in accretionary complexes. In addition to the transect sites, a fifth site (U1328) was established at a cold vent with active fluid flow. The four transect sites represent different typical geological environments of <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence across the northern Cascadia margin from the earliest occurrence on the westernmost first accreted ridge (Site U1326) to the eastward limit of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence in shallower water (Site U1329). Expedition 311 complements previous <span class="hlt">gas</span> <span class="hlt">hydrate</span> studies along the Cascadia accretionary complex, especially ODP Leg 146 and Leg 204 by extending the aperture of the transect sampled and introducing new tools to systematically quantify the <span class="hlt">gas</span> <span class="hlt">hydrate</span> content of the sediments. Among the most significant findings of the expedition was the occurrence of up to 20 m thick sand-rich turbidite intervals with <span class="hlt">gas</span> <span class="hlt">hydrate</span> concentrations locally exceeding 50% of the pore space at Sites U1326 and U1327. Moreover, these anomalous <span class="hlt">gas</span> <span class="hlt">hydrate</span> intervals occur at unexpectedly shallow depths of 50-120 metres below seafloor, which is the opposite of what was expected from previous models of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation in accretionary complexes, where <span class="hlt">gas</span> <span class="hlt">hydrate</span> was predicted to be more concentrated near the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone just above the bottom-simulating reflector. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> appears to be mainly concentrated in turbidite sand layers. During Expedition 311, the visual correlation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> with sand layers was clearly and repeatedly documented, strongly supporting the importance of grain size in controlling <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence. The results from the transect sites provide evidence for a structurally complex, lithology-controlled <span class="hlt">gas</span> <span class="hlt">hydrate</span> environment on the northern Cascadia margin. Local shallow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B11B0014W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B11B0014W"><span>Instrumented Pressure Testing Chamber (IPTC) Characterization of Methane <span class="hlt">Gas</span> <span class="hlt">Hydrate</span>-Bearing Pressure Cores Collected from the Methane Production Test Site in the Eastern Nankai Trough, Offshore Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waite, W. F.; Santamarina, J. C.; Dai, S.; Winters, W. J.; Yoneda, J.; Konno, Y.; Nagao, J.; Suzuki, K.; Fujii, T.; Mason, D. H.; Bergeron, E.</p> <p>2014-12-01</p> <p>Pressure cores obtained at the Daini-Atsumi Knoll in the eastern Nankai Trough, the site of the methane <span class="hlt">hydrate</span> production test completed by the Methane <span class="hlt">Hydrate</span> <span class="hlt">Resources</span> in Japan (MH21) project in March 2013, were recovered from ~300 meters beneath the sea floor at close to in situ pressure. Cores were subsequently stored at ~20 MPa and ~5°C, which maintained <span class="hlt">hydrate</span> in the cores within stability conditions. Pressure core physical properties were measured at 10 MPa and ~6°C, also within the methane <span class="hlt">hydrate</span> stability field, using the IPTC and other Pressure Core Characterization Tools (PCCTs). Discrete IPTC measurements were carried out in strata ranging from silty sands to clayey silts within the turbidite sequences recovered in the cores. As expected, <span class="hlt">hydrate</span> saturations were greatest in more permeable coarser-grained layers. Key results include: 1) Where <span class="hlt">hydrate</span> saturation exceeded 40% in sandy sediments, the <span class="hlt">gas</span> <span class="hlt">hydrate</span> binds sediment grains within the matrix. The pressure core analyses yielded nearly in situ mechanical properties despite the absence of effective stress in the IPTC. 2) In adjacent fine-grained sediment (<span class="hlt">hydrate</span> saturation < 15%), <span class="hlt">hydrate</span> did not significantly bind the sediment. IPTC results in these locations were consistent with the zero effective-stress limit of comparable measurements made in PCCT devices that are designed to restore the specimen's in situ effective stress. In sand-rich intervals with high <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations, the measured compressional and shear wave velocities suggest that <span class="hlt">hydrate</span> acts as a homogeneously-distributed, load-bearing member of the bulk sediment. The sands with high <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations were prone to fracturing (brittle failure) during insertion of the cone penetrometer and electrical conductivity probes. Authors would like to express their sincere appreciation to MH21 and the Ministry of Economy, Trade and Industry for permitting this work to be disclosed at the 2014 Fall AGU meeting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036613','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036613"><span>High-resolution well-log derived dielectric properties of <span class="hlt">gas-hydrate</span>-bearing sediments, Mount Elbert <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stratigraphic Test Well, Alaska North Slope</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sun, Y.; Goldberg, D.; Collett, T.; Hunter, R.</p> <p>2011-01-01</p> <p>A dielectric logging tool, electromagnetic propagation tool (EPT), was deployed in 2007 in the BPXA-DOE-USGS Mount Elbert <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stratigraphic Test Well (Mount Elbert Well), North Slope, Alaska. The measured dielectric properties in the Mount Elbert well, combined with density log measurements, result in a vertical high-resolution (cm-scale) estimate of <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation. Two <span class="hlt">hydrate</span>-bearing sand reservoirs about 20 m thick were identified using the EPT log and exhibited <span class="hlt">gas-hydrate</span> saturation estimates ranging from 45% to 85%. In <span class="hlt">hydrate</span>-bearing zones where variation of hole size and oil-based mud invasion are minimal, EPT-based <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation estimates on average agree well with lower vertical resolution estimates from the nuclear magnetic resonance logs; however, saturation and porosity estimates based on EPT logs are not reliable in intervals with substantial variations in borehole diameter and oil-based invasion.EPT log interpretation reveals many thin-bedded layers at various depths, both above and below the thick continuous <span class="hlt">hydrate</span> occurrences, which range from 30-cm to about 1-m thick. Such thin layers are not indicated in other well logs, or from the visual observation of core, with the exception of the image log recorded by the oil-base microimager. We also observe that EPT dielectric measurements can be used to accurately detect fine-scale changes in lithology and pore fluid properties of <span class="hlt">hydrate</span>-bearing sediments where variation of hole size is minimal. EPT measurements may thus provide high-resolution in-situ <span class="hlt">hydrate</span> saturation estimates for comparison and calibration with laboratory analysis. ?? 2010 Elsevier Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23B1993Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23B1993Y"><span>The influence of sedimentation rate variation on the occurrence of methane <span class="hlt">hydrate</span> crystallized from dissolved methane in marine <span class="hlt">gas</span> <span class="hlt">hydrate</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yuncheng, C.; Chen, D.</p> <p>2015-12-01</p> <p>Methane is commonly delivered to the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone by advection of methane-bearing fluids, diffusion of dissolved methane, and in-situ biogenic methane production (Davie and Buffett, 2003), except at cold vent sites. Burial of pore water and sediment compaction can induce the fluid flux change (Bhatnagar et al., 2007). Sedimentation supply the organic material for methane production. In addition, <span class="hlt">Gas</span> <span class="hlt">hydrate</span> can move to below <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone and decompose via sedimentation. Therefore, sedimentation significantly affect the <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation. ODP site 997 located at the Blake Ridge. The sedimentation rate is estimated to 48 m/Ma, 245m/Ma, 17.2 m/Ma and 281m/Ma for 0-2.5Ma, 2.5-3.75Ma, 3.75-4.4Ma, and 4.4-5.9Ma, respectively, according to the age-depth profile of biostratigraphic marker of nonnofossils(Paull et al., 1996). We constructed a <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation model and apply to ODP sites 997 to evaluate the influence of variation of sedimentation rate on <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulation. Our results show that the <span class="hlt">gas</span> <span class="hlt">hydrate</span> format rate varied from 0.013mol/m2-a to 0.017mol/m2-a and the <span class="hlt">gas</span> <span class="hlt">hydrate</span> burial to below <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone varied from 0.001mol/m2-a to 0.018mol/m2-a during recently 5Ma. The <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation rate by pore water advection and dissolved methane diffusion would be lower, and the top occurrence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> would be shallower, when the sedimentation rate is higher. With higher sedimentation rate, the amount of <span class="hlt">gas</span> <span class="hlt">hydrate</span> burial to below stability zone would be larger. The relative high sedimentation rate before 2.5 Ma at ODP site 997 produced the <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation much lower than present value, and over 60% of present <span class="hlt">gas</span> <span class="hlt">hydrates</span> are formed during recent 2.5Ma. <span">Reference: Bhatnagar,G., Chapman, W. G.,Dickens, G. R., et al. Generalization of <span class="hlt">gas</span> <span class="hlt">hydrate</span> distribution and saturation in marine sediments by scaling of thermodynamic and transport processes. American Journal of Science, 2007, 307, 861</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70186668','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70186668"><span>Widespread <span class="hlt">gas</span> <span class="hlt">hydrate</span> instability on the upper U.S. Beaufort margin</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.</p> <p>2014-01-01</p> <p>The most climate-sensitive methane <span class="hlt">hydrate</span> deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to <span class="hlt">gas</span> <span class="hlt">hydrate</span> dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope <span class="hlt">gas</span> <span class="hlt">hydrates</span> and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope <span class="hlt">gas</span> <span class="hlt">hydrate</span> distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating <span class="hlt">gas</span> <span class="hlt">hydrates</span> into the sediments underlying an area of ~5–7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.8594P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.8594P"><span>Widespread <span class="hlt">gas</span> <span class="hlt">hydrate</span> instability on the upper U.S. Beaufort margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.</p> <p>2014-12-01</p> <p>The most climate-sensitive methane <span class="hlt">hydrate</span> deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to <span class="hlt">gas</span> <span class="hlt">hydrate</span> dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope <span class="hlt">gas</span> <span class="hlt">hydrates</span> and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope <span class="hlt">gas</span> <span class="hlt">hydrate</span> distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating <span class="hlt">gas</span> <span class="hlt">hydrates</span> into the sediments underlying an area of ~5-7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20397674','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20397674"><span>Inhibition of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span> in the presence of liquid hydrocarbons forming structure H.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Seo, Yutaek; Kang, Seong-Pil; Jang, Wonho; Kim, Seonwook</p> <p>2010-05-13</p> <p>The effects of LMGS (large molecule guest substance) amount on the thermodynamics of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span>, as well as structural characteristics of mixed <span class="hlt">hydrates</span> of LMGS and natural <span class="hlt">gas</span>, have been studied. The addition of 1.7 wt % neohexane (NH) to water induced inhibition of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span>, and this inhibition effect increased with increased addition of NH up to 7.8 wt %. However, the <span class="hlt">hydrate</span> equilibrium condition changed slightly when the concentration of NH further increased from 7.8 to 14.5 wt %. Investigations on structural characteristics were carried out by analyzing (13)C NMR spectra of mixed <span class="hlt">hydrates</span> formed from the mixture of natural <span class="hlt">gas</span> and NH. They indicate that two <span class="hlt">hydrate</span> structures of II and H coexist simultaneously, and the ratio of structure H to II decreased from 0.97 to 0.43 when the NH concentration decreased from 14.5 to 7.8 wt %. In addition, it was confirmed that ethane, propane, and iso-butane <span class="hlt">gas</span> molecules do not participate in the formation of structure H and only enclathrated in large cages of structure II. These results indicate the existence of multiple <span class="hlt">hydrate</span> structures, which must be considered in many industrial applications when mixed <span class="hlt">hydrates</span> are formed from multicomponent <span class="hlt">gas</span> mixtures and liquid hydrocarbons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19921885','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19921885"><span>Pure SF6 and SF6-N2 mixture <span class="hlt">gas</span> <span class="hlt">hydrates</span> equilibrium and kinetic characteristics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Eun Kyung; Lee, Ju Dong; Lee, Hyun Ju; Lee, Bo Ram; Lee, Yoon Seok; Kim, Soo Min; Park, Hye Ok; Kim, Young Seok; Park, Yeong-Do; Kim, Yang Do</p> <p>2009-10-15</p> <p>Sulfur hexafluoride (SF6), whether pure or mixed with inexpensive inert <span class="hlt">gas</span>, has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate and/or collect it from waste <span class="hlt">gas</span> streams. In this study, we investigated the pure SF6 and SF6-N2 mixture <span class="hlt">gas</span> <span class="hlt">hydrates</span> formation equilibrium aswell asthe <span class="hlt">gas</span> separation efficiency in the <span class="hlt">hydrate</span> process. The equilibrium pressure of SF6-N2 mixture <span class="hlt">gas</span> was higher than that of pure SF6 <span class="hlt">gas</span>. Phase equilibrium data of SF6-N2 mixture <span class="hlt">gas</span> was similar to SF6 rather than N2. The kinetics of SF6-N2 mixture <span class="hlt">gas</span> was controlled by the amount of SF6 at the initial <span class="hlt">gas</span> composition as well as N2 <span class="hlt">gas</span> incorporation into the S-cage of structure-II <span class="hlt">hydrate</span> preformed by the SF6 <span class="hlt">gas</span>. Raman analysis confirmed the N2 <span class="hlt">gas</span> incorporation into the S-cage of structure-II <span class="hlt">hydrate</span>. The compositions in the <span class="hlt">hydrate</span> phase were found to be 71, 79, 80, and 81% of SF6 when the feed <span class="hlt">gas</span> compositions were 40, 65, 70, and 73% of SF6, respectively. The present study provides basic information for the separation and purification of SF6 from mixed SF6 <span class="hlt">gas</span> containing inert gases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41.6841W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41.6841W"><span>Dynamic morphology of <span class="hlt">gas</span> <span class="hlt">hydrate</span> on a methane bubble in water: Observations and new insights for <span class="hlt">hydrate</span> film models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.</p> <p>2014-10-01</p> <p>Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of <span class="hlt">hydrate</span> on rising bubbles that can enhance their survival in the water column, allowing <span class="hlt">gas</span> to reach shallower depths and the atmosphere. The precise nature and influence of <span class="hlt">hydrate</span> coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble <span class="hlt">hydrate</span> formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, <span class="hlt">hydrate</span> morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between <span class="hlt">hydrate</span> coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse <span class="hlt">gas</span> budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27228750','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27228750"><span>[Raman Characterization of <span class="hlt">Hydrate</span> Crystal Structure Influenced by Mine <span class="hlt">Gas</span> Concentration].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Bao-yong; Zhou, Hong-ji; Wu, Qiang; Gao, Xia</p> <p>2016-01-01</p> <p>CH4 /C2H6/N2 mixed <span class="hlt">hydrate</span> formation experiments were performed at 2 degrees C and 5 MPa for three different mine <span class="hlt">gas</span> concentrations (CH4/C2H6/N2, G1 = 54 : 36 : 10, G2 = 67.5 : 22.5 : 10, G3 = 81 : 9 : 10). Raman spectra for <span class="hlt">hydration</span> products were obtained by using Microscopic Raman Spectrometer. <span class="hlt">Hydrate</span> structure is determined by the Raman shift of symmetric C-C stretching vibration mode of C2H6 in the <span class="hlt">hydrate</span> phase. This work is focused on the cage occupancies and <span class="hlt">hydration</span> numbers, calculated by the fitting methods of Raman peaks. The results show that structure I (s I) <span class="hlt">hydrate</span> forms in the G1 and G2 <span class="hlt">gas</span> systems, while structure II (s II) <span class="hlt">hydrate</span> forms in the G3 <span class="hlt">gas</span> system, concentration variation of C2H6 in the <span class="hlt">gas</span> samples leads to a change in <span class="hlt">hydrate</span> structure from s I to s II; the percentages of CH4 and C2H6 in s I <span class="hlt">hydrate</span> phase are less affected by the concentration of <span class="hlt">gas</span> samples, the percentages of CH4 are respectively 34.4% and 35.7%, C2H6 are respectively 64.6% and 63.9% for <span class="hlt">gas</span> systems of G1 and G2, the percentages of CH4 and 2 H6 are respectively 73.5% and 22.8% for <span class="hlt">gas</span> systems of G3, the proportions of object molecules largely depend on the <span class="hlt">hydrate</span> structure; CH4 and C2H6 molecules occupy 98%, 98% and 92% of the large cages and CH4 molecules occupy 80%, 60% and 84% of the small cages for <span class="hlt">gas</span> systems of G1, G2 and G3, respectively; additionally, N2 molecules occupy less than 5% of the small cages is due to its weak adsorption ability and the lower partial pressure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......201A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......201A"><span>Amplitude vs. Offset Effects on <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> at Woolsey Mound, Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Walter R., Jr.</p> <p></p> <p>Due to the estimated massive quantities of natural methane <span class="hlt">hydrates</span>, they represent one of the largest sources of future alternative energy on Earth. Methane <span class="hlt">hydrates</span> have been found in the shallow sub-seafloor of the Northern Gulf of Mexico where the water depth is in excess of ~900 m. Mississippi Canyon Block 118 has been chosen by the Gulf of Mexico <span class="hlt">Hydrates</span> Research Consortium to be the site of a multi-sensor, multi-discipline sea-floor observatory for <span class="hlt">gas</span> <span class="hlt">hydrate</span> research. First evidence for <span class="hlt">gas</span> <span class="hlt">hydrates</span> at MC 118 was observed at Woolsey Mound. Subsurface evidence for <span class="hlt">gas</span> <span class="hlt">hydrates</span> has subsequently been substantiated by 3D seismic reflection data and piston coring. It is estimated that methane trapped within <span class="hlt">gas</span> <span class="hlt">hydrates</span> worldwide may exceed 1016 kg, one of the largest sources of hydrocarbons to date, and here they present an opportunity for exploitation via harvesting for energy production. The analysis of the 3-D seismic reflection data and integration with industry well logs reveals the subsurface structural and stratigraphic architecture of a thermogenic <span class="hlt">hydrate</span> system in the Mississippi Canyon area (MC-118) of the Gulf of Mexico. Like many hydrocarbon systems in the Gulf of Mexico, Woolsey Mound is dominated by the presence and sporadic movement of allochthonous salt within the sedimentary section. Exploration-scale 3-D seismic imaging shows a network of faults connecting the mound to a salt diapir and an extended area of high P-wave velocity just beneath the sea floor. <span class="hlt">Gas</span> <span class="hlt">hydrates</span> exhibit clear seismic properties such as the bottom simulating reflector (BSR), relatively high P- and S- wave velocities, seismic blanking, and amplitude vs. offset (AVO) effects. These effects occur mainly due to the presence of free <span class="hlt">gas</span> that is usually trapped by the more rigid overlying <span class="hlt">hydrate</span> formations. In order to substantiate the presence of <span class="hlt">hydrates</span> in the shallow subsurface at Woolsey Mound, an AVO analysis based on the variation of the P-wave reflection coefficient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS22B..05R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS22B..05R"><span>Preferential accumulation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in the Andaman accretionary wedge and relationship to anomalous porosity preservation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rose, K.; Torres, M. E.; Johnson, J. E.; Hong, W.; Giosan, L.; Solomon, E. A.; Kastner, M.; Cawthern, T.; Long, P.; Schaef, T.</p> <p>2015-12-01</p> <p>In the marine environment, sediments in the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone often correspond to slope and basin settings. These settings are dominantly composed of fine-grained silt and clay lithofacies with typically low vertical permeability, and pore fluids frequently under-saturated with respect to methane. As a result, the pressure-temperature conditions requisite for a GHSZ to be present occur widely worldwide across marine settings, however, the distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in these settings is neither ubiquitous nor uniform. This study uses sediment core and borehole related data recovered by drilling at Site 17 in the Andaman Sea during the Indian National <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Program Expedition 1 in 2006, to investigate reservoir-scale controls on <span class="hlt">gas</span> <span class="hlt">hydrate</span> distribution. In particular, this study finds that conditions beyond reservoir pressure, temperature, salinity, and <span class="hlt">gas</span> concentration, appear to influence the concentration of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in host sediments. Using field-generated datasets along with newly acquired sedimentology, physical property, imaging and geochemical data with mineral saturation and ion activity products of key mineral phases such as amorphous silica and calcite, we document the presence and nature of secondary precipitates that contributed to anomalous porosity preservation at Site 17 in the Andaman Sea. This study demonstrates the importance of grain-scale subsurface heterogeneities in controlling the occurrence and distribution of concentrated <span class="hlt">gas</span> <span class="hlt">hydrate</span> accumulations in marine sediments, and document the importance that increased permeability and enhanced porosity play in supporting <span class="hlt">gas</span> concentrations sufficient to support <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation. This illustrates the complex balance and lithology-driven controls on <span class="hlt">hydrate</span> accumulations of higher concentrations and offers insights into what may control the occurrence and distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in other sedimentary settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5753228','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5753228"><span>Study of heat transfer characteristics during dissociation of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in porous media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kamath, V.A.</p> <p>1984-01-01</p> <p>An experimental technique was developed to measure the rate of formation and dissociation of <span class="hlt">hydrates</span> in porous media. In the first phase of the work, <span class="hlt">hydrates</span> of propane and methane were studied. Propane <span class="hlt">hydrate</span> cores were formed by contacting liquid propane with compacted porous ice cores at 274 K for 24 to 100 hours, whereas the formation of methane <span class="hlt">hydrates</span> was achieved by contacting ice cores with gaseous methane at about 7000 kPa and 274 K, for 24 to 200 hours. These <span class="hlt">hydrate</span> cores were dissociated by circulating warm water over the top of the core, under controlled temperatures and pressures. The major findings of these experiments are as follows: 1) the phenomena of dissociation of <span class="hlt">hydrates</span> to liquid water and <span class="hlt">gas</span> is similar to nucleate boiling of liquids; 2) the rate of dissociation of <span class="hlt">hydrates</span> at constant ..delta..T, is directly proportional to the area of <span class="hlt">hydrates</span> exposed to the warm fluid or the composition of <span class="hlt">hydrates</span> in the core; and 3) the rate of heat transfer and dissociation increase with increase in pressure and the rate of circulation of the warm fluid. Unified correlations for heat transfer and dissociation rates were successfully obtained for both methane and propane <span class="hlt">hydrate</span> dissociation. These correlations will be useful to predict the rate of dissociation and <span class="hlt">gas</span> production in <span class="hlt">hydrate</span> reservoirs. In the second phase of his work, in order to simulate the conditions of <span class="hlt">hydrate</span> dissociation in the earth, methane <span class="hlt">hydrates</span> were formed and dissociated in unconsolidated cores of sand. The results of these experiments have demonstrated that the heat transfer resistance of the media (rock) plays an important role in dissociation of <span class="hlt">hydrates</span> in earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26488661','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26488661"><span>Structural Basis for the Inhibition of <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> by α-Helical Antifreeze Proteins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Tianjun; Davies, Peter L; Walker, Virginia K</p> <p>2015-10-20</p> <p>Kinetic <span class="hlt">hydrate</span> inhibitors (KHIs) are used commercially to inhibit <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and growth in pipelines. However, improvement of these polymers has been constrained by the lack of verified molecular models. Since antifreeze proteins (AFPs) act as KHIs, we have used their solved x-ray crystallographic structures in molecular modeling to explore <span class="hlt">gas</span> <span class="hlt">hydrate</span> inhibition. The internal clathrate water network of the fish AFP Maxi, which extends to the protein's outer surface, is remarkably similar to the {100} planes of structure type II (sII) <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The crystal structure of this water web has facilitated the construction of in silico models for Maxi and type I AFP binding to sII <span class="hlt">hydrates</span>. Here, we have substantiated our models with experimental evidence of Maxi binding to the tetrahydrofuran sII model <span class="hlt">hydrate</span>. Both in silico and experimental evidence support the absorbance-inhibition mechanism proposed for KHI binding to <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Based on the Maxi crystal structure we suggest that the inhibitor adsorbs to the <span class="hlt">gas</span> <span class="hlt">hydrate</span> lattice through the same anchored clathrate water mechanism used to bind ice. These results will facilitate the rational design of a next generation of effective green KHIs for the petroleum industry to ensure safe and efficient hydrocarbon flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4624156','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4624156"><span>Structural Basis for the Inhibition of <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> by α-Helical Antifreeze Proteins</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sun, Tianjun; Davies, Peter L.; Walker, Virginia K.</p> <p>2015-01-01</p> <p>Kinetic <span class="hlt">hydrate</span> inhibitors (KHIs) are used commercially to inhibit <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and growth in pipelines. However, improvement of these polymers has been constrained by the lack of verified molecular models. Since antifreeze proteins (AFPs) act as KHIs, we have used their solved x-ray crystallographic structures in molecular modeling to explore <span class="hlt">gas</span> <span class="hlt">hydrate</span> inhibition. The internal clathrate water network of the fish AFP Maxi, which extends to the protein’s outer surface, is remarkably similar to the {100} planes of structure type II (sII) <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The crystal structure of this water web has facilitated the construction of in silico models for Maxi and type I AFP binding to sII <span class="hlt">hydrates</span>. Here, we have substantiated our models with experimental evidence of Maxi binding to the tetrahydrofuran sII model <span class="hlt">hydrate</span>. Both in silico and experimental evidence support the absorbance-inhibition mechanism proposed for KHI binding to <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Based on the Maxi crystal structure we suggest that the inhibitor adsorbs to the <span class="hlt">gas</span> <span class="hlt">hydrate</span> lattice through the same anchored clathrate water mechanism used to bind ice. These results will facilitate the rational design of a next generation of effective green KHIs for the petroleum industry to ensure safe and efficient hydrocarbon flow. PMID:26488661</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6263555','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6263555"><span>Geological occurrence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> at the Blake Outer Ridge, western North Atlantic</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dominic, K.L.; Barlow, D.L.</p> <p>1986-03-01</p> <p>The occurrence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> at the Blake Outer Ridge, as confirmed by the Deep Sea Drilling Project (DSDP), is governed not only by <span class="hlt">gas</span>-water phase relationships but also by interrelated geological constraints. The results of this reexamination of the DSDP data show that seafloor processes, topography, and sediment properties are among the factors that impact the stability and distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> at the ridge. Rapid sedimentation and erosion have local and transient effects on thermal gradients, which cause the base of the <span class="hlt">hydrate</span> stability zone to migrate. To a large degree, the convex shape of the Blake Outer Ridge allows <span class="hlt">gas</span> <span class="hlt">hydrates</span> to be stable. Low-permeability sediments occupy the interval in which the stability zone exists, and they influence <span class="hlt">hydrate</span> occurrence by controlling the distribution of <span class="hlt">gas</span>. A brief comparison of the Blake Outer Ridge with two more recently confirmed <span class="hlt">hydrate</span> localities (the northern Gulf of Mexico and the Middle America's trench) shows little similarity among the three <span class="hlt">hydrate</span> environments, but calls attention to the complex and often subtle effects that the geological system imposes on <span class="hlt">hydrate</span> stability. 47 refs., 8 figs., 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.........2F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.........2F"><span>Multi-scale Analysis of Methane <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Formation and Dissociation via Point Source Thermal Stimulation and Carbon Dioxide Exchange</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fitzgerald, Garrett Christopher</p> <p></p> <p> close attention to the distribution of heat during thermal stimulation as a result of the development of high convective transport that occurs in the near vicinity of the heater and in the dissociated <span class="hlt">hydrate</span> zone. This work provides supportive evidence that thermal based <span class="hlt">hydrate</span> dissociation can be achieved with relatively high production efficiencies and satisfactory <span class="hlt">resource</span> recovery potentials. Further, the CH4-CO2 <span class="hlt">gas</span> exchange process was successfully coupled with point source thermal stimulation and the influence of injection rate and heating rate on carbon storage potential and methane recovery potential has been demonstrated.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7310374','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7310374"><span>Evaluation of the geological relationships to <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and stability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krason, J.; Finley, P.</p> <p>1988-01-01</p> <p>The summaries of regional basin analyses document that potentially economic accumulations of <span class="hlt">gas</span> <span class="hlt">hydrates</span> can be formed in both active and passive margin settings. The principal requirement for <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation in either setting is abundant methane. Passive margin sediments with high sedimentation rates and sufficient sedimentary organic carbon can generate large quantities of biogenic methane for <span class="hlt">hydrate</span> formation. Similarly, active margin locations near a terrigenous sediment source can also have high methane generation potential due to rapid burial of adequate amounts of sedimentary organic matter. Many active margins with evidence of <span class="hlt">gas</span> <span class="hlt">hydrate</span> presence correspond to areas subject to upwelling. Upwelling currents can enhance methane generation by increasing primary productivity and thus sedimentary organic carbon. Structural deformation of the marginal sediments at both active and passive sites can enhance <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation by providing pathways for migration of both biogenic and thermogenic <span class="hlt">gas</span> to the shallow <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone. Additionally, conventional hydrocarbon traps may initially concentrate sufficient amounts of hydrocarbons for subsequent <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020216','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020216"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> formation in the deep sea: In situ experiments with controlled release of methane, natural <span class="hlt">gas</span>, and carbon dioxide</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brewer, P.G.; Orr, F.M.; Friederich, G.; Kvenvolden, K.A.; Orange, D.L.</p> <p>1998-01-01</p> <p>We have utilized a remotely operated vehicle (ROV) to initiate a program of research into <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation in the deep sea by controlled release of hydrocarbon gases and liquid CO2 into natural sea water and marine sediments. Our objectives were to investigate the formation rates and growth patterns of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in natural systems and to assess the geochemical stability of the reaction products over time. The novel experimental procedures used the carrying capacity, imaging capability, and control mechanisms of the ROV to transport <span class="hlt">gas</span> cylinders to depth and to open valves selectively under desired P-T conditions to release the <span class="hlt">gas</span> either into contained natural sea water or into sediments. In experiments in Monterey Bay, California, at 910 m depth and 3.9??C water temperature we find <span class="hlt">hydrate</span> formation to be nearly instantaneous for a variety of gases. In sediments the pattern of <span class="hlt">hydrate</span> formation is dependent on the pore size, with flooding of the pore spaces in a coarse sand yielding a <span class="hlt">hydrate</span> cemented mass, and <span class="hlt">gas</span> channeling in a fine-grained mud creating a veined <span class="hlt">hydrate</span> structure. In experiments with liquid CO2 the released globules appeared to form a <span class="hlt">hydrate</span> skin as they slowly rose in the apparatus. An initial attempt to leave the experimental material on the sea floor for an extended period was partially successful; we observed an apparent complete dissolution of the liquid CO2 mass, and an apparent consolidation of the CH4 <span class="hlt">hydrate</span>, over a period of about 85 days.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT........44N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT........44N"><span>Characterizing the accumulation and distribution of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in marine sediments using numerical models and seismic data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nimblett, Jillian Nicole</p> <p></p> <p>Despite the increasing availability of geophysical, geochemical, geotechnical, and biological data that characterize in situ properties of <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs, the fundamental physical processes associated with <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation, accumulation, distribution and dissociation in porous marine sediments remain poorly understood. This study focuses on the spatial and temporal accumulation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> in marine sediments through (1) a numerical model that explores the impact of hydraulic parameters on permeability evolution during <span class="hlt">hydrate</span> formation; and (2) tomographic analysis of multichannel seismic data that constrain the local concentration of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The results constrain the hydraulic parameters pertinent to the hydrodynamics of <span class="hlt">gas</span> <span class="hlt">hydrate</span> reservoirs and provide insight about the physical and elastic properties of <span class="hlt">gas</span> <span class="hlt">hydrate</span> bearing sediments relevant for estimating <span class="hlt">hydrate</span> concentration in porous assemblages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017065','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017065"><span>Seismic character of <span class="hlt">gas</span> <span class="hlt">hydrates</span> on the Southeastern U.S. continental margin</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lee, M.W.; Hutchinson, D.R.; Agena, W.F.; Dillon, William P.; Miller, J.J.; Swift, B.A.</p> <p>1994-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> are stable at relatively low temperature and high pressure conditions; thus large amounts of <span class="hlt">hydrates</span> can exist in sediments within the upper several hundred meters below the sea floor. The existence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> has been recognized and mapped mostly on the basis of high amplitude Bottom Simulating Reflections (BSRs) which indicate only that an acoustic contrast exists at the lower boundary of the region of <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability. Other factors such as amplitude blanking and change in reflection characteristics in sediments where a BSR would be expected, which have not been investigated in detail, are also associated with <span class="hlt">hydrated</span> sediments and potentially disclose more information about the nature of hydratecemented sediments and the amount of <span class="hlt">hydrate</span> present. Our research effort has focused on a detailed analysis of multichannel seismic profiles in terms of reflection character, inferred distribution of free <span class="hlt">gas</span> underneath the BSR, estimation of elastic parameters, and spatial variation of blanking. This study indicates that continuous-looking BSRs in seismic profiles are highly segmented in detail and that the free <span class="hlt">gas</span> underneath the <span class="hlt">hydrated</span> sediment probably occurs as patches of <span class="hlt">gas</span>-filled sediment having variable thickness. We also present an elastic model for various types of sediments based on seismic inversion results. The BSR from sediments of high ratio of shear to compressional velocity, estimated as about 0.52, encased in sediments whose ratios are less than 0.35 is consistent with the interpretation of gasfilled sediments underneath <span class="hlt">hydrated</span> sediments. This model contrasts with recent results in which the BSR is explained by increased concentrations of <span class="hlt">hydrate</span> near the base of the <span class="hlt">hydrate</span> stability field and no underlying free <span class="hlt">gas</span> is required. ?? 1994 Kluwer Academic Publishers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1039916','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1039916"><span><span class="hlt">Hydration</span> of <span class="hlt">gas</span>-phase ytterbium ion complexes studied by experiment and theory</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rutkowski, Philip X; Michelini, Maria C.; Bray, Travis H.; Russo, Nino; Marcalo, Joaquim; Gibson, John K.</p> <p>2011-02-11</p> <p><span class="hlt">Hydration</span> of ytterbium (III) halide/hydroxide ions produced by electrospray ionization was studied in a quadrupole ion trap mass spectrometer and by density functional theory (DFT). <span class="hlt">Gas</span>-phase YbX{sub 2}{sup +} and YbX(OH){sup +} (X = OH, Cl, Br, or I) were found to coordinate from one to four water molecules, depending on the ion residence time in the trap. From the time dependence of the <span class="hlt">hydration</span> steps, relative reaction rates were obtained. It was determined that the second <span class="hlt">hydration</span> was faster than both the first and third <span class="hlt">hydrations</span>, and the fourth <span class="hlt">hydration</span> was the slowest; this ordering reflects a combination of insufficient degrees of freedom for cooling the hot monohydrate ion and decreasing binding energies with increasing <span class="hlt">hydration</span> number. <span class="hlt">Hydration</span> energetics and <span class="hlt">hydrate</span> structures were computed using two approaches of DFT. The relativistic scalar ZORA approach was used with the PBE functional and all-electron TZ2P basis sets; the B3LYP functional was used with the Stuttgart relativistic small-core ANO/ECP basis sets. The parallel experimental and computational results illuminate fundamental aspects of <span class="hlt">hydration</span> of f-element ion complexes. The experimental observations - kinetics and extent of <span class="hlt">hydration</span> - are discussed in relationship to the computed structures and energetics of the <span class="hlt">hydrates</span>. The absence of pentahydrates is in accord with the DFT results, which indicate that the lowest energy structures have the fifth water molecule in the second shell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AIPC.1027..869R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AIPC.1027..869R"><span>In Situ Formation and Evolution of <span class="hlt">Gas</span> <span class="hlt">Hydrates</span> in Water-in-Oil Emulsions Using Pressure Rheometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rensing, P. J.; Liberatore, M. W.; Tonmukayakul, N.; Koh, C. A.; Sloan, E. D.</p> <p>2008-07-01</p> <p>In oil and <span class="hlt">gas</span> production and transportation a major concern is the formation of <span class="hlt">gas</span> <span class="hlt">hydrates</span> (crystalline <span class="hlt">gas</span>-water inclusion compounds that are stable at high pressures and low temperatures). <span class="hlt">Gas</span> <span class="hlt">hydrates</span> have a tenacious ability to plug pipelines, and may lead to unscheduled shut downs. The successful operation of pipeline transport with <span class="hlt">gas</span> <span class="hlt">hydrates</span> particles will depend on the ability to control <span class="hlt">gas</span> <span class="hlt">hydrate</span> agglomerations and depositions. <span class="hlt">Gas</span> <span class="hlt">hydrates</span> can be thermodynamically inhibited but this is proving cost ineffective and environmentally unfriendly. For this reason the oil/<span class="hlt">gas</span> industry is moving to <span class="hlt">hydrate</span> management rather than traditional methods of thermodynamic inhibition. One intriguing possibility would be to convert the water in the pipelines to non-agglomerating <span class="hlt">gas</span> <span class="hlt">hydrates</span> and then flow the slurry. However, this cannot be reliably achieved until basic understanding of <span class="hlt">hydrate</span> slurry rheology is gained. To develop this fundamental understanding, in situ pressurized <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and rheological measurements from a water-in-oil emulsion have been conducted. In this work, small amplitude oscillatory and steady shear techniques have been used to characterize the rheological properties of these systems. The results demonstrate that <span class="hlt">hydrate</span> formation can be detected in steady shear and oscillatory measurements, where a large viscosity (and elastic modulus) increase coincides with <span class="hlt">hydrate</span> formation. Since temperature and pressure affect the thermodynamic stability of <span class="hlt">hydrates</span> these are particular key variables that need to be tuned for this system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/978801','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/978801"><span>Application of fiber optic temperature and strain sensing technology to <span class="hlt">gas</span> <span class="hlt">hydrates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ulrich, Shannon M; Madden, Megan Elwood; Rawn, Claudia J; Szymcek, Phillip; Phelps, Tommy Joe</p> <p>2008-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> may have a significant influence on global carbon cycles due to their large carbon storage capacity in the form of greenhouse gases and their sensitivity to small perturbations in local conditions. Characterizing existing <span class="hlt">gas</span> <span class="hlt">hydrate</span> and the formation of new <span class="hlt">hydrate</span> within sediment systems and their response to small changes in temperature and pressure is imperative to understanding how this dynamic system functions. Fiber optic sensing technology offers a way to measure precisely temperature and strain in harsh environments such as the seafloor. Recent large-scale experiments using Oak Ridge National Laboratory's Seafloor Process Simulator were designed to evaluate the potential of fiber optic sensors to study the formation and dissociation of <span class="hlt">gas</span> <span class="hlt">hydrates</span> in 4-D within natural sediments. Results indicate that the fiber optic sensors are so sensitive to experimental perturbations (e.g. refrigeration cycles) that small changes due to <span class="hlt">hydrate</span> formation or dissociation can be overshadowed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.754d2011M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.754d2011M"><span>Intensification of <span class="hlt">hydrate</span> formation by means of explosive boiling incipience of rarefied <span class="hlt">gas</span> in a bulk of water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mezentsev, I. V.; Meleshkin, A. V.; Elistratov, D. S.; Elistratov, S. L.; Mutali, M. N.</p> <p>2016-10-01</p> <p>The experiments on obtaining <span class="hlt">gas</span> <span class="hlt">hydrate</span> of refrigerant 134a were carried out by the method, based on explosive boiling-up of a layer of liquefied <span class="hlt">gas</span> in a bulk of water at decompression. It is shown that this method combines several factors, leading to intensification of <span class="hlt">hydrate</span> formation process, resulting in the fast <span class="hlt">gas</span> <span class="hlt">hydrate</span> growth. The effect of the decompression rate on the volume of produced <span class="hlt">hydrate</span> was studied experimentally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19105749','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19105749"><span>The carbon dioxide-water interface at conditions of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lehmkühler, Felix; Paulus, Michael; Sternemann, Christian; Lietz, Daniela; Venturini, Federica; Gutt, Christian; Tolan, Metin</p> <p>2009-01-21</p> <p>The structure of the carbon dioxide-water interface was analyzed by X-ray diffraction and reflectivity at temperature and pressure conditions which allow the formation of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. The water-gaseous CO2 and the water-liquid CO2 interface were examined. The two interfaces show a very different behavior with respect to the formation of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. While the liquid-<span class="hlt">gas</span> interface exhibits the formation of thin liquid CO2 layers on the water surface, the formation of small clusters of <span class="hlt">gas</span> <span class="hlt">hydrate</span> was observed at the liquid-liquid interface. The data obtained from both interfaces points to a <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation process which may be explained by the so-called local structuring hypothesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25388796','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25388796"><span>Abnormal incorporation of amino acids into the <span class="hlt">gas</span> <span class="hlt">hydrate</span> crystal lattice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sa, Jeong-Hoon; Kwak, Gye-Hoon; Lee, Bo Ram; Ahn, Docheon; Lee, Kun-Hong</p> <p>2014-12-28</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> are crystalline ice-like solid materials enclosing <span class="hlt">gas</span> molecules inside. The possibility of the presence of <span class="hlt">gas</span> <span class="hlt">hydrates</span> with amino acids in the universe is of interest when revealing the potential existence of life as they are evidence of a source of water and organic precursors, respectively. However, little is known about how they can naturally coexist, and their crystallization behavior would become far more complex as both crystallize with formation of hydrogen bonds. Here, we report abnormal incorporation of amino acids into the <span class="hlt">gas</span> <span class="hlt">hydrate</span> crystal lattice that is contrary to the generally accepted crystallization mode, and this resulted in lattice distortion and expansion. The present findings imply the potential for their natural coexistence by sharing the crystal lattice, and will be helpful for understanding the role of additives in the <span class="hlt">gas</span> <span class="hlt">hydrate</span> crystallization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23B2001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23B2001K"><span>Acoustic Investigations of <span class="hlt">Gas</span> and <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Formations, Offshore Southwestern Black Sea*</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kucuk, H. M.; Dondurur, D.; Ozel, O.; Atgin, O.; Sinayuc, C.; Merey, S.; Parlaktuna, M.; Cifci, G.</p> <p>2015-12-01</p> <p>The Black Sea is a large intercontinental back-arc basin with relatively high sedimentation rate. The basin was formed as two different sub-basins divided by Mid-Black Sea Ridge. The ridge is completely buried today and the Black Sea became a single basin in the early Miocene that is currently anoxic. Recent acoustic investigations in the Black Sea indicate potential for <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation and <span class="hlt">gas</span> venting. A total of 2500 km multichannel seismic, Chirp sub-bottom profiler and multibeam bathymetry data were collected during three different expeditions in 2010 and 2012 along the southwestern margin of the Black Sea. Box core sediment samples were collected for <span class="hlt">gas</span> cromatography analysis. Wide spread BSRs and multiple BSRs are observed in the seismic profiles and may be categorized into two different types: cross-cutting BSRs (transecting sedimentary strata) and amplitude BSRs (enhanced reflections). Both types mimic the seabed reflection with polarity reversal. Some undulations of the BSR are observed along seismic profiles probably caused by local pressure and/or temperature changes. Shallow <span class="hlt">gas</span> sources and chimney vents are clearly indicated by bright reflection anomalies in the seismic data. <span class="hlt">Gas</span> cromatography results indicate the presence of methane and various components of heavy hydrocarbons, including Hexane. These observations suggest that the <span class="hlt">gas</span> forming <span class="hlt">hydrate</span> in the southwestern Black Sea may originate from deeper thermogenic hydrocarbon sources. * This study is supported by 2214-A programme of The Scientific and Technological Research Council of Turkey (TÜBITAK).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21707093','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21707093"><span>High-pressure <span class="hlt">gas</span> <span class="hlt">hydrates</span> of argon: compositions and equations of state.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Manakov, Andrey Yu; Ogienko, Andrey G; Tkacz, Marek; Lipkowski, Janusz; Stoporev, Andrey S; Kutaev, Nikolay V</p> <p>2011-08-11</p> <p>Volume changes corresponding to transitions between different phases of high-pressure argon <span class="hlt">gas</span> <span class="hlt">hydrates</span> were studied with a piston-cylinder apparatus at room temperature. Combination of these data with the data taken from the literature allowed us to obtain self-consistent set of data concerning the equations of state and compositions of the high-pressure <span class="hlt">hydrates</span> of argon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70094795','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70094795"><span>Methane <span class="hlt">Hydrates</span>: Chapter 8</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Boswell, Ray; Yamamoto, Koji; Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott</p> <p>2008-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrate</span> is a solid, naturally occurring substance consisting predominantly of methane <span class="hlt">gas</span> and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that <span class="hlt">gas</span> can be extracted from <span class="hlt">gas</span> <span class="hlt">hydrates</span> with existing production technologies, particularly for those deposits in which the <span class="hlt">gas</span> <span class="hlt">hydrate</span> exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional <span class="hlt">resource</span> assessments indicate that substantial volumes of <span class="hlt">gas</span> <span class="hlt">hydrate</span> likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from <span class="hlt">gas-hydrate</span>-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce <span class="hlt">gas</span> from select <span class="hlt">gas</span> <span class="hlt">hydrate</span> deposits. In addition, substantial additional volumes of <span class="hlt">gas</span> <span class="hlt">hydrate</span> have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine <span class="hlt">resource</span> volumes within potential accumulations that can be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/873892','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/873892"><span>Method for the photocatalytic conversion of <span class="hlt">gas</span> <span class="hlt">hydrates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Taylor, Charles E.; Noceti, Richard P.; Bockrath, Bradley C.</p> <p>2001-01-01</p> <p>A method for converting methane <span class="hlt">hydrates</span> to methanol, as well as hydrogen, through exposure to light. The process includes conversion of methane <span class="hlt">hydrates</span> by light where a radical initiator has been added, and may be modified to include the conversion of methane <span class="hlt">hydrates</span> with light where a photocatalyst doped by a suitable metal and an electron transfer agent to produce methanol and hydrogen. The present invention operates at temperatures below 0.degree. C., and allows for the direct conversion of methane contained within the <span class="hlt">hydrate</span> in situ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24985860','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24985860"><span>Measurements of <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation probability distributions on a quasi-free water droplet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Maeda, Nobuo</p> <p>2014-06-01</p> <p>A High Pressure Automated Lag Time Apparatus (HP-ALTA) can measure <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation probability distributions from water in a glass sample cell. In an HP-ALTA <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation originates near the edges of the sample cell and <span class="hlt">gas</span> <span class="hlt">hydrate</span> films subsequently grow across the water-guest <span class="hlt">gas</span> interface. It would ideally be desirable to be able to measure <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation probability distributions of a single water droplet or mist that is freely levitating in a guest <span class="hlt">gas</span>, but this is technically challenging. The next best option is to let a water droplet sit on top of a denser, immiscible, inert, and wall-wetting hydrophobic liquid to avoid contact of a water droplet with the solid walls. Here we report the development of a second generation HP-ALTA which can measure <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation probability distributions of a water droplet which sits on a perfluorocarbon oil in a container that is coated with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane. It was found that the <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation probability distributions of such a quasi-free water droplet were significantly lower than those of water in a glass sample cell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6997066','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6997066"><span><span class="hlt">Gas</span> <span class="hlt">hydrate</span> that breaches the sea floor on the continental slope of the Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>MacDonald, I.R.; Guinasso, N.L. Jr.; Sassen, R.; Brooks, J.M.; Lee, L. ); Scott, K.T. )</p> <p>1994-08-01</p> <p>We report observations that concern formation and dissociation of <span class="hlt">gas</span> <span class="hlt">hydrate</span> near the sea floor at depths of [minus]540 m in the northern Gulf of Mexico. In August 1992, three lobes of <span class="hlt">gas</span> <span class="hlt">hydrate</span> were partly exposed beneath a thin layer of sediment. By May 1993, the most prominent lobe had evidently broken free and floated away, leaving a patch of disturbed sediment and exposed <span class="hlt">hydrate</span>. The underside of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> was about 0.2[degree]C warmer than ambient sea water and had trapped a large volume of oil and free <span class="hlt">gas</span>. An in situ monitoring device, deployed on a nearby bed of mussels, recorded sustained releases of <span class="hlt">gas</span> during a 44 day monitoring period. <span class="hlt">Gas</span> venting coincided with a temporary rise in water temperature of 1[degree]C, which is consistent with thermally induced dissociation of <span class="hlt">hydrate</span> composed mainly of methane and water. We conclude that the effects of accumulating buoyant force and fluctuating water temperature cause shallow <span class="hlt">gas</span> <span class="hlt">hydrate</span> alternately to check and release <span class="hlt">gas</span> venting. 18 refs., 3 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70134770','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70134770"><span>Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 <span class="hlt">gas-hydrate</span>-bearing cores</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stern, Laura A.; Lorenson, T.D.</p> <p>2014-01-01</p> <p>We report on grain-scale characteristics and <span class="hlt">gas</span> analyses of <span class="hlt">gas-hydrate</span>-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and <span class="hlt">gas</span> chromatography, we investigated <span class="hlt">gas</span> <span class="hlt">hydrate</span> grain morphology and distribution within sediments, <span class="hlt">gas</span> <span class="hlt">hydrate</span> composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> in KG-basin samples commonly occurs as nodules or coarse veins with typical <span class="hlt">hydrate</span> grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free <span class="hlt">gas</span> phase. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit <span class="hlt">gas</span> <span class="hlt">hydrate</span> grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original <span class="hlt">hydrate</span> formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where <span class="hlt">gas</span> <span class="hlt">hydrate</span> fills microfossil crevices. The range of <span class="hlt">gas</span> <span class="hlt">hydrate</span> modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The <span class="hlt">hydrate</span>-forming <span class="hlt">gas</span> is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the <span class="hlt">gas</span> <span class="hlt">hydrate</span> is Structure I.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C33A0700K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C33A0700K"><span>Preliminary Experimental Examination Of Controls On Methane Expulsion During Melting Of Natural <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kneafsey, T. J.; Flemings, P. B.; Bryant, S. L.; You, K.; Polito, P. J.</p> <p>2013-12-01</p> <p>Global climate change will cause warming of the oceans and land. This will affect the occurrence, behavior, and location of subseafloor and subterranean methane <span class="hlt">hydrate</span> deposits. We suggest that in many natural systems local salinity, elevated by <span class="hlt">hydrate</span> formation or freshened by <span class="hlt">hydrate</span> dissociation, may control <span class="hlt">gas</span> transport through the <span class="hlt">hydrate</span> stability zone. We are performing experiments and modeling the experiments to explore this behavior for different warming scenarios. Initially, we are exploring <span class="hlt">hydrate</span> association/dissociation in saline systems with constant water mass. We compare experiments run with saline (3.5 wt. %) water vs. distilled water in a sand mixture at an initial water saturation of ~0.5. We increase the pore fluid (methane) pressure to 1050 psig. We then stepwise cool the sample into the <span class="hlt">hydrate</span> stability field (~3 degrees C), allowing methane <span class="hlt">gas</span> to enter as <span class="hlt">hydrate</span> forms. We measure resistivity and the mass of methane consumed. We are currently running these experiments and we predict our results from equilibrium thermodynamics. In the fresh water case, the modeled final <span class="hlt">hydrate</span> saturation is 63% and all water is consumed. In the saline case, the modeled final <span class="hlt">hydrate</span> saturation is 47%, the salinity is 12.4 wt. %, and final water saturation is 13%. The fresh water system is water-limited: all the water is converted to <span class="hlt">hydrate</span>. In the saline system, pore water salinity is elevated and salt is excluded from the <span class="hlt">hydrate</span> structure during <span class="hlt">hydrate</span> formation until the salinity drives the system to three phase equilibrium (liquid, <span class="hlt">gas</span>, <span class="hlt">hydrate</span>) and no further <span class="hlt">hydrate</span> forms. In our laboratory we can impose temperature gradients within the column, and we will use this to investigate equilibrium conditions in large samples subjected to temperature gradients and changing temperature. In these tests, we will quantify the <span class="hlt">hydrate</span> saturation and salinity over our meter-long sample using spatially distributed temperature sensors, spatially distributed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS43F..02E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS43F..02E"><span>Joint Electrical and Seismic Interpretation of <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Bearing Sediments From the Cascadia Margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ellis, M.; Minshull, T.; Sinha, M.; Best, A.</p> <p>2008-12-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrates</span> are found in continental margin sediments worldwide. Their global importance as future energy reserves and their potential impact on slope stability and abrupt climate change all require better knowledge of where they occur and how much <span class="hlt">hydrate</span> is present. However, current estimates of the distribution and volume of <span class="hlt">gas</span> <span class="hlt">hydrate</span> beneath the seabed range widely. Improved geophysical methods could provide much better constraints on <span class="hlt">hydrate</span> concentrations. Geophysical measurements of seismic velocity and electrical resistivity using seabed or borehole techniques are often used to determine the <span class="hlt">hydrate</span> saturation of sediments. <span class="hlt">Gas</span> <span class="hlt">hydrates</span> are well known to affect these physical properties; <span class="hlt">hydrate</span> increases sediment p-wave velocity and electrical resistivity by replacing the conductive pore fluids, by cementing grains together and by blocking pores. A range of effective medium theoretical models have been developed to interpret these measurements in terms of <span class="hlt">hydrate</span> content, but uncertainties about the pore-scale distribution of <span class="hlt">hydrate</span> can lead to large uncertainties in the results. This study developed effective medium models to determine the seismic and electrical properties of <span class="hlt">hydrate</span> bearing sediments in terms of their porosity, micro-structure and <span class="hlt">hydrate</span> saturation. The seismic approach combines a Self Consistent Approximation (SCA) and Differential Effective Medium (DEM), which can model a bi-connected effective medium and allows the shape and alignment of the grains to be taken into account. The electrical effective medium method was developed to complement the seismic models and is based on the application of a geometric correction to the Hashin-Shrikman conductive bound. The electrical and seismic models are non-unique and hence it was necessary to develop a joint electrical and seismic interpretation method to investigate <span class="hlt">hydrate</span> bearing sediments. The joint method allows two variables (taken from porosity, aspect ratio or <span class="hlt">hydrate</span> saturation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA218418','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA218418"><span><span class="hlt">Gas</span> <span class="hlt">Hydrate</span> and Acoustically Laminated Sediments: Potential Environmental Cause of Anomalously Low Acoustic Bottom Loss in Deep-Ocean Sediments</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1990-02-09</p> <p>saturation. One volume of water commonly binds from 70 to 220 volumes of <span class="hlt">gas</span>. Voids in the atomic lattice of <span class="hlt">hydrate</span> become increasingly occupied at lnwer...<span class="hlt">gas</span> <span class="hlt">hydrates</span> are expected in nature. Structure I <span class="hlt">hydrates</span>, which are less densely packed structures that accommodate varying <span class="hlt">gas</span> molecule atomic radii...paraffin series natural <span class="hlt">gas</span> and other gases in relation to atomic size of molecules. The largest allowable size of <span class="hlt">gas</span> molecules that can be incorporated</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27170363','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27170363"><span>Changes in microbial communities associated with <span class="hlt">gas</span> <span class="hlt">hydrates</span> in subseafloor sediments from the Nankai Trough.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Katayama, Taiki; Yoshioka, Hideyoshi; Takahashi, Hiroshi A; Amo, Miki; Fujii, Tetsuya; Sakata, Susumu</p> <p>2016-08-01</p> <p>Little is known about the microbial distribution patterns in subseafloor sediments. This study examines microbial diversity and activities in sediments of the Nankai Trough, where biogenic <span class="hlt">gas</span> <span class="hlt">hydrates</span> are deposited. Illumina sequencing of 16S rRNA genes revealed that the prokaryotic community structure is correlated with <span class="hlt">hydrate</span> occurrence and depth but not with the sedimentary facies. The bacterial phyla 'Atribacteria' lineage JS1 and Chloroflexi dominated in all samples, whereas lower taxonomic units of Chloroflexi accounted for community variation related to <span class="hlt">hydrate</span> saturation. In archaeal communities, 'Bathyarchaeota' was significantly abundant in the <span class="hlt">hydrate</span>-containing samples, whereas Marine Benthic Group-B dominated in the upper sediments without <span class="hlt">hydrates</span>. mcrA gene sequences assigned to deeply branching groups and ANME-1 were detected only in <span class="hlt">hydrate</span>-containing samples. A predominance of hydrogenotrophic methanogens, Methanomicrobiales and Methanobacteriales, over acetoclastic methanogens was found throughout the depth. Incubation tests on <span class="hlt">hydrate</span>-containing samples with a stable isotope tracer showed anaerobic methane oxidation activities under both low- and seawater-like salinity conditions. These results indicate that the distribution patterns of microorganisms involved in carbon cycling changed with <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence, possibly because of the previous <span class="hlt">hydrate</span> dissociation followed by pore water salinity decrease in situ, as previously proposed by a geochemical study at the study site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1051648','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1051648"><span>Contribution of oceanic <span class="hlt">gas</span> <span class="hlt">hydrate</span> dissociation to the formation of Arctic Ocean methane plumes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reagan, M.; Moridis, G.; Elliott, S.; Maltrud, M.</p> <p>2011-06-01</p> <p>Vast quantities of methane are trapped in oceanic <span class="hlt">hydrate</span> deposits, and there is concern that a rise in the ocean temperature will induce dissociation of these <span class="hlt">hydrate</span> accumulations, potentially releasing large amounts of carbon into the atmosphere. Because methane is a powerful greenhouse <span class="hlt">gas</span>, such a release could have dramatic climatic consequences. The recent discovery of active methane <span class="hlt">gas</span> venting along the landward limit of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone (GHSZ) on the shallow continental slope (150 m - 400 m) west of Svalbard suggests that this process may already have begun, but the source of the methane has not yet been determined. This study performs 2-D simulations of <span class="hlt">hydrate</span> dissociation in conditions representative of the Arctic Ocean margin to assess whether such <span class="hlt">hydrates</span> could contribute to the observed <span class="hlt">gas</span> release. The results show that shallow, low-saturation <span class="hlt">hydrate</span> deposits, if subjected to recently observed or future predicted temperature changes at the seafloor, can release quantities of methane at the magnitudes similar to what has been observed, and that the releases will be localized near the landward limit of the GHSZ. Both gradual and rapid warming is simulated, along with a parametric sensitivity analysis, and localized <span class="hlt">gas</span> release is observed for most of the cases. These results resemble the recently published observations and strongly suggest that <span class="hlt">hydrate</span> dissociation and methane release as a result of climate change may be a real phenomenon, that it could occur on decadal timescales, and that it already may be occurring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPA....6h5317V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPA....6h5317V"><span>Atomistic modeling of structure II <span class="hlt">gas</span> <span class="hlt">hydrate</span> mechanics: Compressibility and equations of state</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D.</p> <p>2016-08-01</p> <p>This work uses density functional theory (DFT) to investigate the poorly characterized structure II <span class="hlt">gas</span> <span class="hlt">hydrates</span>, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of <span class="hlt">gas</span> <span class="hlt">hydrates</span>, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest <span class="hlt">hydrates</span> showing a larger increase than single-guest <span class="hlt">hydrates</span>, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of <span class="hlt">gas</span> <span class="hlt">hydrates</span> to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II <span class="hlt">gas</span> <span class="hlt">hydrates</span>. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036902','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036902"><span>Geologic controls on <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence in the Mount Elbert prospect, Alaska North Slope</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Boswell, R.; Rose, K.; Collett, T.S.; Lee, M.; Winters, W.; Lewis, K.A.; Agena, W.</p> <p>2011-01-01</p> <p>Data acquired at the BPXA-DOE-USGS Mount Elbert <span class="hlt">Gas</span> <span class="hlt">Hydrate</span> Stratigraphic Test Well, drilled in the Milne Point area of the Alaska North Slope in February, 2007, indicates two zones of high <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation within the Eocene Sagavanirktok Formation. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> is observed in two separate sand reservoirs (the D and C units), in the stratigraphically highest portions of those sands, and is not detected in non-sand lithologies. In the younger D unit, <span class="hlt">gas</span> <span class="hlt">hydrate</span> appears to fill much of the available reservoir space at the top of the unit. The degree of vertical fill with the D unit is closely related to the unit reservoir quality. A thick, low-permeability clay-dominated unit serves as an upper seal, whereas a subtle transition to more clay-rich, and interbedded sand, silt, and clay units is associated with the base of <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurrence. In the underlying C unit, the reservoir is similarly capped by a clay-dominated section, with <span class="hlt">gas</span> <span class="hlt">hydrate</span> filling the relatively lower-quality sands at the top of the unit leaving an underlying thick section of high-reservoir quality sands devoid of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. Evaluation of well log, core, and seismic data indicate that the <span class="hlt">gas</span> <span class="hlt">hydrate</span> occurs within complex combination stratigraphic/structural traps. Structural trapping is provided by a four-way fold closure augmented by a large western bounding fault. Lithologic variation is also a likely strong control on lateral extent of the reservoirs, particularly in the D unit accumulation, where <span class="hlt">gas</span> <span class="hlt">hydrate</span> appears to extend beyond the limits of the structural closure. Porous and permeable zones within the C unit sand are only partially charged due most likely to limited structural trapping in the reservoir lithofacies during the period of primary charging. The occurrence of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> within the sands in the upper portions of both the C and D units and along the crest of the fold is consistent with an interpretation that these deposits are converted free <span class="hlt">gas</span> accumulations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036219','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036219"><span>Elevated <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation within silt and silty clay sediments in the Shenhu area, South China Sea</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wang, X.; Hutchinson, D.R.; Wu, S.; Yang, S.; Guo, Y.</p> <p>2011-01-01</p> <p><span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190-221 m below seafloor (mbsf). <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the <span class="hlt">hydrate</span>-bearing sediment zone indicates that <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations above the base of the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone at depths of 190 to 221 mbsf. <span class="hlt">Gas</span> <span class="hlt">hydrate</span> occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced <span class="hlt">gas</span> <span class="hlt">hydrate</span> formation. In addition, <span class="hlt">gas</span> chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the <span class="hlt">gas</span> <span class="hlt">hydrate</span> stability zone which transport methane for the formation of <span class="hlt">gas</span> <span class="hlt">hydrate</span>. Sedimentation and local canyon migration may contribute to higher <span class="hlt">gas</span> <span class="hlt">hydrate</span> saturations near the base of the stability zone. Copyright 2011 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24633777','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24633777"><span>A quantum chemistry study of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Atilhan, Mert; Pala, Nezih; Aparicio, Santiago</p> <p>2014-04-01</p> <p>The structure and properties of natural <span class="hlt">gas</span> <span class="hlt">hydrates</span> containing hydrocarbons, CO₂, and N₂ molecules were studied by using computational quantum chemistry methods via the density functional theory approach. All host cages involved in I, II, and H types structures where filled with hydrocarbons up to pentanes, CO₂ and N₂ molecules, depending on their size, and the structures of these host-guest systems optimized. Structural properties, vibrational spectra, and density of states were analyzed together with results from atoms-in-a-molecule and natural bond orbitals methods. The inclusion of dispersion terms in the used functional plays a vital role for obtaining reliable information, and thus, B97D functional was shown to be useful for these systems. Results showed remarkable interaction energies, not strongly affected by the type of host cage, with molecules tending to be placed at the center of the cavities when host cages and guest molecules cavities are of similar size, but with molecules approaching hexagonal faces for larger cages. Vibrational properties show remarkable features in certain regions, with shiftings rising from host-guest interactions, and useful patterns in the terahertz region rising from water surface vibrations strongly coupled with guest molecules. Likewise, calculations on crystal systems for the I and H types were carried out using a pseudopotential approach combined with Grimme's method to take account of dispersion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70022699','USGSPUBS'); retu